Ah, it was 4/24/2000. I wasn’t sure of the exact date!
For me it’s 21 years, and nearly 1/3rd of my life.
Honestly, it’s been the best era of my life.
March 27, 2000 for me, which puts it at a third of my life. I don’t remember much of the previous two thirds.
I’m shocked- shocked I say! - that I was on the dope for at least 3 years before joining! I can’t even imagine this - I chose my name while in Mississippi, yet they date is when I was in Washington. There must be something weird about joining times. I’m very confused- I know I joined in 1998.
I’ve got a couple months to go yet. Remember when dopefests were a big thing? There seemed to be one going on somewhere nearly every week. I’ve managed to make it to one in 5 different countries.
The current message board only dates from March of 1999. If you were on before that, it was the AOL predecessor.
I joined right after New Year in 2000. I lurked for about 4 months before that. I never even saw the AOL version. In those days, I thought AOL was lame, so I avoided it. Also, even though I knew of the Straight Dope newspaper column since the early 90s, I never actually saw one of them in a newspaper. The local alternative paper didn’t carry it; I learned of the column online.
Weren’t there Straight Dope Usenet newsgroups up by that time too? ISTR browsing those back in the day too, as Y2K approached us in the near distance.
I got turned onto the SD back in the late 70’s when it appeared in Baltimore’s “City Squeeze” alternative newspaper.
Does watching The Straight Dope (starring Mike Lukas) on TV count (A&E Channel)? If so, then I can back-date my Dope-ability to 1997.
BomTek and I did one in Afghanistan. Although we couldn’t call it a “Dope-fest” since there were only two of us. I think we settled on “Dope-shin-dig” due to the limited planned attendance.
Tripler
I’ve done a handful–at least 3 that I can recount: NYC, Georgia, and Tennessee.
My 19-year anniversary will be on Dec 3, 2020. I joined when I was 26. I remember reading the 9/11 posts as it was unfolding, but I didn’t join until a few months later. Not sure how long I lurked, but it was at least three months.
I joined in September '99. I was 37. 
I miss the Dopefests as well. I went to a few in Toronto, though I seem to have missed the early era of healthy debauchery at them.
May I ask why you don’t remember?
Yes, and I was definitely on AOL even though it apparently took 13 months for me to register here. I remember the announcement of moving here and I remember the move, but I apparently didn’t make the move right away. Must have lurked.
Geez, I lurked for years before I joined. But I’ve been lurking since 1997.
I didn’t join until 2003, but that’s still makes just short of 1/3 of my life spent here.
I coulda done worse…