I guess it's not an "age" thing for me, really. If I like a game, there's a good chance I will wander back to it. And there's a good chance I actually finished it in the first place. I may wander back to it months later, a year later, or in the case of Morrowind, a 3 year hiatus and I fired it up again and was just happy being a complete noob, because I had forgotten so much of it. I love Oblivion - it is still installed, but I have not touched it in over a year now. I may one day.

If an older game (or a more recent game, for that matter) is entertaining, but does not grip me the way a small handful of games can do, then I will happily play it, possibly finish it... and just move on, probably never think about playing it again, sometimes give them away, etc.

I am actually the same way with books - there are certain books I re-read periodically because I just love them. Not every few months of course, but every couple of years. And I enjoy the story so much, that I love going through it again. Not a lot of books do that for me, but the ones that do... same with games - I love going back to them, even if its only for a little while.