My experience is similar to Jependlton's: I've got scores of LPs that I bought new in the 60's and 70's that still sound great. I also recommend use of a wet-vac cleaning machine and a carbon fiber brush before *and* after each play.
How long should vinyl last?
Say I found a prestine copy of Sgt. Pepper's Lonely Heart Club Band. It was brand new and never opened. If I play it on a state of the art turntable, how many years of play can I get out of it if I play it once a week and take excellent care of it? How long before the initial crispness disappears?