Wait until you start picking an age in the future and then you count back and think about what you was doing then. For me lets say 65, takes me back to 39, the things I did then seem just a few years ago.
I'm only 28 and I suck at keeping in touch with people - of all the great people I've met over the years I have one close friend who I speak to most days, but other than that I have about half a dozen people I'll see a couple of times a year.
I don't really know how it happens, I love going out with people - but don't seem to get around to calling somebody and then it's been years and you feel like you've passed the point where you can.
I recently bumped into a guy I used to hang about with most of the time, we barely had two words to say to each other - it took me by surprise that we moved on so much
Since getting married and having kids I've seen (as I'm sure most people do in this situation) a rapid fall off in the amount of going out time you get. I've lost contact with a few friends that facebook has gone some way to rectify, but like Dan I can go months, in some cases years without seeing people. Most of my friends are still people I've known from school and we've not moved on at all! It's great when we all get together, it's like no time has passed since we last met and can sit for hours talking about nothing in particular. It's hard making new friends though, probably because I know I can rely on that group and probably don't try hard enough when meeting new people...
bastard by name