With my old account I just used it to keep track of my favorites. That was about 2 years of lurking. With my new account I started using the forums right away.
I lurked for 2 months after my last frequently-used site got shut down on the licensing crackdown. I got sent this way on the site's chat while I was a complete and total noob to h-mangas and doujins. So much of a noob in fact, that I was still thinking that I "wasn't normal" for liking WINcest doujins. I'm still a noob to it all, but I'm learning.
I initially made an account with the first username I could think of, hence the Gmod idiot box reference as mine, to take advantage of the favourites feature. I got curious and wanted to introduce myself to the community, and I made my first real comment which was my M&G thread.
I joined maybe a month or two after stumbling upon this site. I was motivated to join so that i could comment, then once i joined, I came to the forums maybe a week or 2 later. When i first came here, I didn't even see the home page for at least a week because i came from a link off of google that went straight to a manga. I wasn't worried about what the site was or looked like, I was too busy browsing lolz. But eventually i checked everything out and now i'm here.
I've been a lurker for 3-4 years, I think, it sounds about right to me haha. I didn't check the site for a long time, and kinda forgot about it until a friend linked me to a doujinshi about a year ago. ^^;