Reptile Relief can be applied every 3 days according to the directions. It's not a pesticide, it's a salt solution that works by dehydrating the mites that come into contact with it. Unfortunately once it dries it loses much of its efficacy, and unfortunately it causes crappy sheds because it dehydrates your snake's skin as well.

If you haven't treated the tubs with PAM you also need to do that in addition to the paper. Same goes for the rack if you're using one, the mites will lay eggs in the crevices. You can put your snakes in a lukewarm bath with a small drop of dish soap, which will help drown the mites, while you're treating their tubs and rack.

A cheaper alternative to PAM is the 2 oz bottle of NIX or RID head lice treatment (listed as 1% permethrin). Combine the 2 oz bottle with a gallon of water, put into a spray bottle, and use like you would the PAM.

If you can secure the cats outside of the room for a few hours, hang a Hot Shot No-Pest strip in the room and close the door. I do it for 12-24 hours at a time. Remove the water bowls while the strips are in use, the pesticide has a strong affinity for water and you don't want the snakes ingesting it. After 12-24 hours put the strip into an airtight container such as a zip-lock bag, air out the room, and put the water bowls back into the tubs with fresh water. Repeat weekly. Some people cut the strip up and put it into containers in the tubs, I just treat the room as a whole.

Good luck and even once you stop seeing mites continue to treat for them for at least 30 days to make sure you don't miss any eggs that are slow to hatch out, as the eggs are tough and the pesticides don't kill them.