I'm amazed at how many topics are going on over there, but the vast majority of participants are in just a few. I usually just check new posts to see if there's anything of interest. I guess I check 3 or 4 forums. This is still my favorite.
I think Phils trailer sailor forum is also on this format. Is that busier? I worry that you can lose a specific density of posters to a forum. After that it shrinks quickly. We may not be there, but I suspect we're close.