I fucking hate it when people do this. Why are you bothering? It's a thought experiment, not a plan of action.

Just accept the terms and come to a conclusion, that way you actually fill the requirements of the discussion.

He might as well be asking what would happen to water if it became cardboard.

It's an impossibility because I have access to the database and can erase any record of a ban from the back end. Even if someone were able to remove my admin powers, I could go in and change them back in the database. Besides that, I make backups of the database and forum structure so things could be restored.

But ignoring all that, I'd say no more than three weeks (maybe a month). It would take a while, but eventually the mods would start getting banned and word would catch on that the forum is sinking; the angry, angry Offtopic members would swarm with clusters of spam and it would soon be abandoned.