24 rounds of combat is a really long time... A Wizard at 18th level could cast a melfs acid arrow 7 times and do an automatic 196d4 damage over 98 rounds that are without save! heheh. Who cares if its that much damage over a certain amount of time. its also long enough for the bad guy you are facing to have a dispel magic cast on him before he bites the bullet.
jake
jake