First there's your first few posts or threads where you write paragraphs just to get every topic off your chest. Considering this is such an open-minded forum, anything goes (within ethical reason). This allows people to just finally have that venue.
Later, people start posting into as many forums and topics as possible. Until eventually (once you're on long enough) things just seem predictable as newer people show up... and the cycle continues.
I've definitely experienced this. Two or three times now I've just grown tired of these forums and the interminable repetition...but that's sort of the nature of the beast. I'll disappear for a while, or just go in to lurker mode, and then after long enough the winds change and the topics get more interesting again.
I've noticed that the section I now return to last is "Sex With A Large Penis". I find it the most repetitive (circumcision and quasi-incest threads aside), but likely the most appealing to new members. This is, after all a large-penis support group, even though I doubt that most of the people on here actually have large penises (which is fine by me - don't get me wrong). Relationships, Discrimination, Health, Appearance Issues...those are things that I think can sustain more interesting and more long-term conversations, and those are the places I find myself coming back to.
One thing I'm glad LPSG has taught me is to write on the internet the way I would speak in real life. If I'd be too chickenshit to say it to someone's face, I'd be a total douche to say it on the internet - and if I'm too chickenshit to say it to someone's face I should probably examine where that thought is coming from as it probably says more about me than it does about the truth.
But why I really like LPSG, the main reason I keep coming back, is being able to be helpful. Getting a "thank you" for good advice is a great ego-boost and a good indicator that, even on the internet, you can help someone out when they're unsure of what to do next.