Wal now, I'm only almost-forty (another couple of weeks), so I'm not in a position to judge the older years, but believe me, I wouldn't take under-thirty again for anything. And as for eighteen--ugh!!! No, I'm looking forward to post-menopause and hoping for a long cronehood.
But songs, now:
Stan Rogers' "Lies," about an aging ranch wife looking in her mirror, is probably the most compassionate song I've heard in my life.
On the rowdier side, filker/folker Michael Longcor's got a wonderful one about "I can't party as hearty as I partied/When I partied at 21." Chorus goes something like:
Well, I've drunk with Jose Cuervo,
Had a dance with Irish Rose;
Went two-out-of-three with old Jack D
And I think he broke my nose.
(And as a last line, after all the drinking memories, he adds in a suggestive voice: "But there's one or two things I do a whole lot better/Than when I was 21!")
And is it CSN&Y or EL&P who did "Wasted on the Way?"
So much time to make up, everywhere you turn,
Time we have wasted on the way,
So much water moving underneath the bridge;
Let the water come and carry us away.