I joined when I was 9 (1999). I got REALLY into it, then after being scammed, went the scammer/hacker route. I remember hacking into an account with a 10mil bank balance. Best day of my Neopian life lol. (but now that I'm a mature, conscientious adult - ha - I don't do that stuff anymore)
I usually get really into it for awhile, get frozen or bored with it, then take a year or so off. It always lures me back in, though....usually when I just have a lot of free time on my hands.