I joined either 1996 or 1997, and don't remember which for sure. I could figure it out if I had to: I went online with my A500 and bought my A2000, so if I could figure out when I started using that, I'd be close!
I'm not using the same account because originally the account name was required to be an email address. At some point, they switched to requiring an account name and not allowing it to be an email address. When they did that, for some reason instead of keeping my original account and changing the user name, I abandoned my account and started a new one some time later. I have no recollection of why that was.
My current account started 25 November 1998. I have 219 feedback, mostly buying, some selling. My score is 100% even though in the past it wasn't. I've had non-paying buyers leave me negative feedback, and also a couple sellers who claimed I didn't pay.