There is no American music with a longer history of fandom than country western (jazz is a close second). I used to follow a country discussion group. It was interesting to see how what people considered "real" country music was always the music they grew up listening to. For older fans, Hank Williams was authentic country. For a later generation, it was George Jones (or George Strait a bit later). Then Garth Brooks, etc. Even though there was good (authentic) music made before and after their faves, what they were weaned on defined what was "true" country.

Of course, the same thing holds true with pop, rock, r&b, rap, etc. The only people who don't seem to moor themselves to their 10-30 years are musicians themselves. I think they're always looking for something new, and most of them realize that their identity is also closely linked to past trends before they started listening. Musicians also tend to be far less concerned with genre and style than do their fans.