Say I have the edit time limit for a user group set to 2400 minutes, but on one forum I want to reduce that to 2 minutes. It seems I can't make that happen as the longer time limit set for that group globally overrides the one I set on a per forum basis.
OK, it would be good to be able to override that with a lower value when necessary.
e.g. there is a forum where people advertise stuff for sale. It is a bad idea for them to be able to edit Ads after a sale as they could edit the description after the purchaser buys something which is not good, however it would be nice if they can edit their fist post for a couple of minutes in cases of typos or or other mistakes.