It's been a while and I'm not 100% sure when people started dropping off. If I'd have to guess, I'd say once school started for everyone at that time, Fall 2004, people started dropping off either that semester or the next, Spring 2005. I'm guessing the reason is either school got in the way or after a while, message boards get kind of old.
If you look at Downy's profile, he logged in last on September 14, 2005, Fall 2005, so I guess he's still around. But i'd have to say it was way earlier than that, when the bulk of the cat fighting came to quick death.
I noticed you are at Michigan? If I remember correctly, I thought that is where Downy is?