Hey, I remember you from the last Lurker Roll call thread! . So your two posts are both in lurker threads… 
As for me, I don’t even remember how long I was lurking before I signed up and posted. But I made my first post in July of '01, and still haven’t broken 250 posts.
Ditto. I read The Straight Dope column in the Portland Phoenix (actual paper version, however) for about 3 years before I decided I’d like to ask a question. Whilst looking for an e-mail address to do so, I discovered the boards and asked in General Questions instead. So I lurked long enough to read the forum descriptions, and that’s about it.