I've often thought about this for various bands, including the BB's and Beatles. My rule of thumb is, if a band, artist or composer is still fairly popular 50 years after their heyday, they'll probably still be listened to and talked about, at least among a narrow audience, 200 years afterwards.
For the most part I expect you're right. Every now and then, an artist can fall into obscurity for a while then interest will be revived; but I think what you say is the general truth.↧