User blog comment:NightChime/Buffs: 2x Max?/@comment-1393900-20110615185831

Unless they change it the ports or in disgaea 3, the max you can get for buffs is a 100% increase and as far as I know INT has no bearing on effectiveness; 20% is 20% no matter what. As for the duration, I do know it slowly wear off after each turn. I don't know if it can transfer between floors, I'm guessing it's not but its should be easy to try though