I think now that I'm mature, I'll probably stay for a long time. I've made a few friends here, and I've met forumers that I admire. I've seen some impressive builds that I wouldn't have normally seen ingame, and this is where I get most of my news. It's always funny when I see a topic about something on the forums, and then a few hours later, my mom tells me about it.
Really, once you get used to them, the community isn't all that bad. I'd assume that the time I leave the forums would be if I were to get perma-banned, the place gets overrun by stupids, it dies of activity, or things just get too busy in life. However, I don't see any of that coming any time soon.