Shame. No US board I know of seems to support out-of-sight-out-of-mind type functionality.
Well, in the cases Fred's addressed publicly, people were getting their knickers in a knot over stuff that was days (and, I believe in some cases, weeks) old. Having a short-lifespan design could possibly eliminate some of that - give people less stuff to piss themselves off over, and they might behave better. Nothing's ever 100%, though; some folks are just bound and determined to be offended, and some topics are almost automatic button-pushers. Keeping a non-topical subforum open will have to be a balance between blandness and riot. As has been noted by some here, most of the general Mac's threads have a long, long history of being non-riotish, so that gives me more hope that they'd tend to be that way than fear that they'd degenerate into snipsnarksnarl. I think if we have something like that but keep a fairly regular eye on it (and maybe address via PM people who look like they're edging towards the Dark Side), it should work.
Still, that requires modding, and we're short-staffed. *shrug* In the end, there's no way to know other than diving in and finding out.