Those dates are chosen on one hand by the raid on the monastery in Lindisfarne, being the "first" viking raid in Britain (or more generally on the 'western route') and on the other end the defeat of the Norwegian king Harald Hardrada at Stamford Bridge.

Already there it's clear these are two entirely different phenomena, the former being a small group of raiders and the latter being more or less a military campaign on the behalf of a consolidated Christian kingdom that had not existed in that sense in 800.

These beginnings and ends are not "sharp" by any account. These were significant events but not culturally defining ones at the time. In fact defining Scandinavian cultures (plural) in terms of individual events in Britain is pretty absurd on its face, and to some extent says something about how the whole viking concept is largely sprung out of Victorian Era romanticism. The term "viking" not used as a group term by historians when talking about Scandinavians of the Viking Age, it's limited to how they used the term themselves, for actual raiders/seafarers/traders. (Except for in marketing. I have this book for instance, which has 'viking' in the title but is not used at all in the text outside a couple mentions in the introduction..)

So the popularization of the 'viking' concept was not based on today's standards of historiography, but the Viking Age concept has still survived - which it did because there are, in fact, cultural changes that occurred in Scandinavia at roughly both ends here. But one should be aware of the term's history and implications (to quote historian Sirpa Aalto: "The Viking Age was politically and ideologically coloured already in the process of identifying it as a distinct and significant period in history" )

So in general Scandinavian historiography, the Viking Age is the last sub-period within the Scandinavian Iron Age, preceding the Scandinavian Middle Ages, and there are cultural changes associated with it. But they were by no means sharp changes. Not at all.

The most significant, if not the driving force, behind the start of the Viking Age is the rise of trading networks in Scandinavia and the greater Baltic area. Already in the 7th century the trading town of Dorestad existed near present day Utrecht, and its size and importance would peak around 800. In the mid 700s, you have the foundation of Staraya Ladoga, on the route from the Baltic south to Novgorod (Holmgarðr in Old Norse) and through various portages one could get to the Dniepr and follow that down to the Black Sea and Constantinople. (or go up the Don and over to the Volga and the Caspian) Wolin was founded on the mouth of the Oder around the same time. The late 700s also sees the founding of Hedeby in Denmark, Birka in Sweden and by 800 or so Skiringssal in Norway. These were the first towns in Scandinavia and functioned as trading posts - likely both being created in response to and catalyzing the trade.

That mean that before or at the same time as the raiding starts, you see a growth here of international trade and travel in Scandinavia and the adjacent areas. This was itself preceded (unclear how long but not more than a century or two) by the adoption of sails. The clinker technique used for shipbuilding had already existed, but the use of sails did not seem to become popular until around the mid-8th century. The Salme ships, found in Estonia and dating to the first half of the 700s were buried with dead Scandinavians thought to have been raiders. The ships themselves were old a the time as they'd had undergone many repairs, and are thought to be late 600s. They were not masted vessels.

So it is not coming out of nowhere. There is a ramping up of trade and foreign travel in general in the century and a half or so preceding the Viking Age. Once farther afoot, they discover "soft targets" like monasteries and churches. Successful raids breed more raids, it quickly becomes popular.

But raiding peaks in the 9th century, and instead you have a shift towards conquest. As is well known, North England was invaded, Rollo (Hrolf) is invited to rule in Normandy, in exchange for protection from raids. At the same time a group of Scandinavians led by Rurik is supposedly invited to come rule what'd become the Rus' kingdom in Novgorod. Although the more likely events are that a urban bourgeoisie of Norse traders arose in towns along the trading route. (much as north German traders of the Hansa would become in later centuries, and along some of the same routes). We can only speculate on this shift, but it seems likely this kind of organized conquest simply rendered a better risk-reward ratio as awareness of and thus preparedness for raids had increased.

Meanwhile, people are coming in contact with Christianity abroad and returning with a new religion. Not counting the mission of Ansgar, which failed to cause any lasting converts, the first Christians seem to turn up around the early 900s. Some traditional benchmarks of conversion are Harald Bluetooth (reigned in the 970s) who supposedly converts Denmark, Iceland decides to convert at a þing meeting dated to 1000, Saint Olaf does so for Norway in the 1010s-20s. No single king is even credited with converting Sweden; the country consisted of two ethnic groups, the Gautar (Geats) in the south had converted earlier than the Svíar (Swedes) and pushing Christianity may have threatened their rule over the latter. A threat made real in a later saga account that king Inge the Elder was deposed by the Svíar in favor of his brother, who'd promised to perform sacrifices. But with the help of Geatish forces, Inge is supposed to have killed his brother around 1087, regained power, and destroyed the pagan temple at Old Uppsala. (The details of this story are not trusted, but one can say that it's quite plausible from other sources that a pagan uprising did occur in the 1080s)

So the mid-1000s is a point in time by which most Scandinavians had nevertheless converted and can work as a book-end in that sense. But there is still no sudden change here. It's not until the late 1000s and 12th c. the earliest monasteries are founded and much of the organization of the church comes into place, such as Scandinavians getting their own archbishops. Slavery/thralldom persists for 2-300 years despite being discouraged by the church. Linguistically, the large amount of German loan words that entered Scandinavian and created much of the distance from Swedish/Danish/Norwegian to Old Norse occurred in the 1300s.

Late Viking Age art styles (which'd never been free of foreign influences anyway) like Urnesstil began to mix with Romaneque and new styles came about. Motifs from Norse sagas continue to appear in art well into the 1200s, which is also when much those sagas are written down. The trend - particularly pronounced in Uppland in Sweden, of carving rune stones really peaked in the mid-11th century as monuments over the dead, while it ended entirely by around 1120 or so. Which has two contradictory consequences - one being that "Viking Age" in the context of categorizing rune stones is a half-century longer, the other being the some would actually put he end of the Viking Age to around 1040-1050 on the basis that there are so many stones after that point, one has entered the historic period. (i.e. where you have written sources)

The end of runestone raising in Uppland corresponds in a change in burial customs, from burying people in Christian graves but in traditional mounds on traditional family grave sites, to burials in church yards with a grave marker. That had itself been preceded by a change to Christian burial customs where the body was not cremated and placed with the head towards the east. Several invasions, smaller scale attempts, were made on England after Stamford Bridge. And it's not long into the 1100s when Scandinavians began raids against their own pagan neighbors that they'd earlier been extracting gelds (tributes) from, but now as crusades.

In terms of political organization, the end of the Viking Age changed nothing - in the short term. On the contrary you could view it as "the calm before the storm". By that point, consolidated countries ruled by kings had emerged, but these kings still had very limited power of their own. Likewise, the church had emerged as a new power source, but had yet to build up significant wealth and political power. The 12th and 13th centuries saw Denmark, Sweden, Norway and even Iceland embroiled in civil wars that saw various constellations of nobles fight for power, for territory for themselves and/or their counties and over the principle of royal vs aristocratic power. With differing results, too. (Royal power enhanced in Norway and the nobility remaining stronger in Sweden and Denmark, the Icelanders lost their independence and became subjects of the King of Norway) Despite having a nobility, feudalism (ill-defined as it is) in a continental West European sense was never introduced. No strict hierarchy of power, no serfdom. Most farmers owned their own soil. Hereditary monarchy and definite royal supremacy over the aristocracy was only really established during the Renaissance.

There's so much romanticizing the Viking Age, many people (particularly outside Scandinavia) who've only interested themselves in that aspect, seem to think that a button was pressed in 1066 and Scandinavians then became 'generic Christian Europeans' (as if such a thing existed). But there was broad cultural continuity both at the start and end of the Viking Age, and there was continual change through it as well. I wouldn't even say that 1066 is an inflection point. In many ways life for the average Norwegian in 1030 was much more similar to 1080 than the latter was to 1180.

TL;DR: I don't think you'll find many historians that are strongly married to either date.