To me, a "classic" album doesn't necessarily have to have that much so-called "lasting power". Any album that is specifically indicative of a stage of my life gets classified as a classic for me. Take Ocean Avenue, for example. Almost everyone on this site would consider it a classic, but if they took a step back and looked at why it was a classic for them, it would be because it was a major part of that stage of their life. And that's my two cents.