That seems to me true, but in a limited way. I also think the material genuinely lives because it is of worth. And I would guess that it's picking up listeners a good deal younger than myself, some a long way from being born when it was originally recorded. Just as I more than happily listen to, say, recordings by Duke Ellington and hear them as something new. In fact, a quick look at reviews of albums at amazon.com and the comments sections under various proggy items uploaded to youtube.com reveals the degree to which younger listeners are a distinct part of the audience with an ear out for these oldies.
So the question I'm asking myself is how long albums produced in the sixties and seventies, to pick out the two decades in which the recording process had become sophisticated enough to routinely ensure first rate recording of a diverse range of talent, are going to be made fairly easily available and have an audience ready to listen to them, and, of course, this goes beyond the rather narrow confines of what was once termed progressive rock. If the answer is forever, or as long as there is a forever, then this will constitute an important cultural shift. The past will always be close behind, nudging up to the present in consoling and depressing ways, telling us that nothing ever ever ever really changes. I suppose that's always been the case, but one never made with quite the kind of immediacy that can get imprinted on a CD.
(And it's just occurred to me - pardon my obtuseness in failing to see the obvious - that we now no longer even need the physical CDs for the music to be readily available. Can it ever go away? Will its lastingness confirm some kind of value being inherent within it?)