Maybe we need a way to filter out threads that contain more than a given number of posts (when viewing "New Posts"). Just as we can say that we only want to see threads from a particular selection of forums, it would be nice if we could say we only want to see threads containing fewer than, say, 30 posts.
That way, the New Posts page wouldn't be constantly cluttered up with the likes of "What is in your cup?" and "The Vent and Rant Thread" and "So what are you doing RIGHT NOW?" and other threads that contain hundreds and thousands of posts.
I tend to agree with Saoir that those threads are pretty useless, except perhaps for the people who participate in them regularly. Nobody is going to wade through page after page of messages in the hope of seeing something useful.
I'm not saying we should ban long discussions, but it would be nice if there was a way to optionally filter them out of the New Posts page.