I'm here, and this site has been very helpful both for information and an audience for thinking out loud. I've done the same on a couple other sites as well.
I think at some point, though, I am likely to evaporate. Not because I'm abandoning transition, the site isn't helpful, or because I have any problems with the people here, though. Just because I am hopeful that transition will not be forever---that the process will reach a conclusion---and I think I will have less interest in talking about some of the topics after that. I suppose it'd be nice to stay around and help n00bs, but I'm not sure whether that's likely to happen for the long term.
I've had this experience with a couple of other forums on other totally unrelated subjects. I would be active for a couple years, rack up a few thousand posts, and then one day just stop checking in. One thing that happens is you lose track of the people who are active, so sometimes a short hiatus can make it hard to return.
My guess is that this is not a rare thing to have happen. It doesn't reflect poorly on the site at all, it is just a result of people essentially getting what they came for and moving on. Probably sometimes it's the reverse---not every forum suits every person, so probably some people find they are more comfortable other places and disappear quickly. Hard to know, but I think it's a normal phenomenon for any sort of long-lived Internet forum.