I have a 'barn door' fixture, a hinged piece of plywood on an exterior wall, to hold the belts while washing. I powerwash them when necessary. I sand a lot of Cocobolo also. It does fine to 80 grit, OK to 100, and starts loading at 120.
Yes, the belts cost a bit to buy, (though for the SDM-15 belts are about $18 each, not expensive) but I do not really notice the cost as they last quite a while as long as I do not burn one through operator error.
These tools MAKE money. Shop time is valuable, should be well in excess of $1/minute for tasks other than 'sweeping the floor'.