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.
You can put stuffed animals in the dryer for 20 minutes in most cases (I have done it for 45 without any melt downs), a black garbage bag for 30 days sealed also works, since the life cycle is no more than 30 days.