I've seens posts bumped after 5 mins or 1 hour.
Most of the forums i've been to (not only games - or even warez - forums) have a rule not to bump be4 24 hours. there was a post selling a mage that was bumped every 5 mins, it even reached 12 pages.
i see that is a busy forum and new posts come every hour, but bumping mindlessly it's just like a lame spaming.
Also i've noticed that on many topics ppl start flaming, maybe a flame room would be nice to settle arguments