I do a complete scrubdown (not just spraying with cleaner and changing the substrate) once a month, weather allowing. We have a hot water hose outside but if it's too cold, I can't really go out there and there's nowhere else inside to do it. I've transitioned solely to newspaper for all my BPs (my sand boa has ground walnut shells) but when I had them on reptibark (which I much prefer, but is of course more expensive) I would only spot-clean. When I scrubbed down their tub, I just threw away the substrate. For me, it seems silly to put dirty substrate (because it is dirty. Spotcleaning the poop or urates doesn't remove the stuff that's been peed on) back into a fresh, clean tub.