I haven't been here that long.
It's on your profile page. Just click on "Read about me" below your profile picture. For you, it's December 5, 2008.
For me, it's October 1, 2010, and I haven't taken any long breaks (more than a week) from wiki editing. Things have been busy.
I joined Feb of 2009 but I really only became active after Gia and John visited the Giant Bomb forums to discuss some misconceptions about the site toward the end of 2009. Sadly, they moved on shortly thereafter, but I stayed because I was at a point in my life where anime was important to me again. Back then I was watching Shakugan no Shana and now that franchise is wrapping up. The circle of life, baby.