I'm new here (1 month) and I have to say that the forums do seem to be less lively than I expected. They do seem active though.

There are a LOT of threads and sub-forums. Each day when I click on "new posts", there are at least a full page of new posts from across all of the forums. So there is activity. If you click into each forum, I can see how you would get the impression that it's dead here, but overall there is a decent amount of activity.

There is a setting that controls how far back in time you will see threads from. By changing this on Control Panel, threads shouldn't disappear on you.