I went to my 20th class reunion and while we (my wife and I) had a nice time, I'm not sure that it was anything to write home about. Some people I remembered, many I didn't. Living out of town now, we really no longer have much in common. Didn't go back for the 25th or 30th or later.

Like I said, it was a nice evening but haven't felt any compelling need to go back. If I still lived there, even, I might.. I think IAKG said it well ... depends on how close you were (and still want to be).