I'm going to read up on this more and maybe flesh out my answer a little later. But my general sense is that there was not a strong sense of generational change along strictly periodic lines (like decades). In part this is because music that didn't keep up with the times was not kept around on "oldies" stations, but simply faded from view. So, you could write a very successful opera in the 1750s which could premiere at Europe's biggest opera house with a stellar cast of world class singers, and then maybe the opera only plays in the circuit for maybe 3 or 4 years before it gets dropped from view and the market moves on. There's simply no market for "the big hits from 10 years ago!"

Which is not to say that things are always forgotten. There are pieces that have a very long afterlife, Handel's Messiah, for instance, has seen pretty much continuous performance since the day it was written. And there are concerts of "Ancient Music" that tend to crop up in English speaking lands that are dedicated to old music. But these are special cases, not the norm. And my sense is that these pieces don't tend to be heard in terms of specific time periods ("oh, that sounds like the 40s!") but rather in terms of being "recognizably out of fashion, but still good enough to warrant continued performances." There's not enough of a circulating repertoire of pieces from, say, the 1740s circulating around in the 1760s to really give people a good sense of "here's what this decade sounded like." You just have these individual pieces that survive here and there, and then the traces that that decade's work have left on the practices of the present.

That said, there are connoisseurs who had a better understanding of this sort of thing. This is the era that Music History emerges in the writings of people like Charles Burney, and I've seen people (like Vogler in the 1770s) compare music from different decades to each other. But these guys are a relatively small bunch of critics, it's hard to say how much that attitude drips down to other kinds of music listeners. Unless you are like a serious music geek with the means to have things copied for your personal collection, your exposure to music is likely what's currently playing at the opera houses and in salons. And, at least until about 1770, you aren't going to hear anything there that's more than about 5 years old or so.

But I'm gonna give the Burney history a read sometime soon and see if he has anything to say about the decades immediately preceding the publication of his book. I'll let you know if I find anything interesting.