I actually didn't start posting for about 2 months after I signed up. From there it's been about a year now.
The real trick is getting a job where you work nights, 12 hours a shift, have at least 3 nights where you do absolutely nothing but surf LQ and TLDP, and getting paid for it all in large swoop.
That, and building a few linux-related projects (my MP3box that I installed in my truck) really helps you to learn the ins and outs so you can answer posts better, and more often. Then you just find the questions you know, go through and answer em.
I think a major contributor to the post count was BigJohn. Me and him have written a saga or 2, one was about getting sound from a cdrom, I think it turned out to be something like 200 posts in the end! Eventually things got worked out, and lucky for me, he still comes back
That, and I like to follow up on most of the questions I respond to, I like to make sure my help, well helped. If it didn't I try to figure out why, find a better answer, reword my existing one, and get the issue worked out. Eventually I ended up with 7 thousand posts, crazy.