You can change how long you want the corpse to stay there with the rules below. That is all I am aware of. As long as there is a corpse that hasn't been rezzed, it will still be rezzable. I don't know of a way to separate how long a corpse stays from how long it can be rezzed for. And if the zone drops and is restarted, it resets all related timers anyway. Unless the zone is set to load statically, then the timers run no matter what.
Character:LeaveCorpses true
Character:LeaveNakedCorpses true
Character
eathExpLossLevel 76
Character:CorpseDecayTimeMS 1800000