As a admin of a dying forum, do you know when it's time to pack up and quit that forum or do you keep working on keeping it open?
If a forum starts failing you know you are doing something wrong, perhaps you can't see what your doing wrong. Bring someone on the team that knows what they are doing if your totally clueless. I generally would up my advertising campaigns, post fresh content and perhaps a new site look.
when to quit, huh? if I own a forum, then I'll never quite. it will die with me, I'd die with it. XD if I'm only part of staff team, I'll quit when I lose motivation to help the forum as a staff member -- something which never happened so far, and I hope I won't. I imagine it to be so terrible. ^^"