The life span of lice depends on how much food there is on the stuffed animal. They will procreate and new lice will hatch. The best solution is to put the toys in a plastic bag and replace them, because not to do this will keep the infestation in the room where the toys are. You could try washing them with lice killing shampoo and see if that works, however, the nits (eggs) are hard to kill.
