Hi there /u/LLuke_

As an undergraduate getting my degree in archaeology I had the same concern you did. I loved archaeology, but it seemed like everything had already been done. As I learned more, I realized that there is still a lot to learn about archaeology, so much that we'll have plenty to research for years to come!

For perspective, I work in the U.S. Southwest (New Mexico, Arizona, Colorado, Utah, and northern Mexico) and this is one of the best researched places on the planet. The only other areas that have had more archaeological research done would be Mexico/Central America, the Andes in South America, Europe, and around the Mediterranean (especially Egypt and anything Roman/Greek). There are more archaeologists in the Southwest than anywhere else in the USA, and they've been working here since the late 1800s.

Even though a lot of archaeologists have been doing a lot of archaeology in the Southwest for more than 100 years, there is still a lot we can learn. Even when archaeologists excavate a site, most of the time they don't excavate the entire site which lets people in the future go back and do more work there. Pueblo Bonito in Chaco Canyon, NM, is probably the most well-excavated site in the Southwest. It was mostly worked at in the early 20th century, but even as recently as 2013 Patricia Crown at University of New Mexico went back to Pueblo Bonito and re-excavated one of the rooms that had been excavated originally in the early 1900s. Between doing this and applying new scientific techniques to artifacts excavated from that room originally she made the discovery that people in Pueblo Bonito had been consuming chocolate, even though the nearest place they could possibly have obtained any chocolate is far to the south in Mexico. This was a totally new discovery about a place that is one of, if not the, most well-researched archaeological site in the entire Southwest!

This is true everywhere in the world. Not only can you go back to sites that have already been excavated and still find new things, but there are plenty of unexcavated sites, and even artifacts from already excavated sites can tell us new things if we apply new scientific techniques to them. Sometimes you can go back and look at work people have previously done and improve on it, either because now you have more information or because you are asking questions the original researchers never thought to ask.

Keep in mind this is also something happening in one of the best researched places on the planet. There are plenty of other places where we can't even answer basic questions about the archaeology! For instance, most of sub-Saharan Africa has very little archaeology done in it compared to the rest of the world despite having a very long history. India, Central Asia, and Iran are also all places with a lot of archaeology but very few archaeologists. Same for the South Pacific.

Basically, don't worry about "running out" of history to study. We have a lot to learn still about even the best researched places on the planet, and there are plenty of places where we haven't even answered basic questions about the archaeology and history yet!