It's not entirely true, y'know, about me doing the "loved it when I was 20 but now I'm old" thing. I got into Dinosaur Jr.'s You're Living All Over Me, for example, at, I think, age 31, and that's an album that would have blown my brains out at age 18. So hey, the Minutemen still have a chance.
Then there are things I end up liking in a new context--like I thought I was over The Wall, but really liked revisiting the movie, and ended up liking The Final Cut now that I'm past 30 as well, an album all the prog nerds from my youth screamed at me to either hate-listen to, or avoid.
And of course, I dig up dumb pop songs from my teen/college years all the time and enjoy them for triggering silly memories of better days. Particularly embarrassing recent examples of this terrible nostalgia phenomenon include the songs Tevin Campbell sang as "Powerline" for A Goofy Movie (don't be surprised to find out how many people love THOSE damned things, Harvey Danger's "Flagpole Sitta," and--oh God, this one's gonna hurt--Hoku's "Perfect Day" from Legally Blonde. YIKES. But it triggers me! I remember hearing it in 2001!