You don't have to strip the stall of all the sawdust everyday. Just pick out the poop and the wet spots. With a foal his size in a stall that size and him not being in all the time I would say take all the sawdust out and put new sawdust in at least.... twice a month. You want to thoroughly pick his stall out. Some of his poop is going to make it's way to the bottom of the sawdust.