Age also plays a vital role in the moulting process .. the bigger/older it gets the longer the time in between moults. Some keepers speed up the process by what is known as "powerfeeding" which can speed up the growth of the spider but can also shorten the life span... as some would say. Another interesting thing is that if a spider looses its leg in a moult(or any other survivable injury) the chances are that the period before the next moult will be very short so that it can heal or regenerate the limb that it lost.