I'd suggest waiting until they shed and then doing a thorough clean. Mine like to take a giant dump after they shed so that's usually when I do my cleaning. I hate fully cleaning a terrarium just to find a little present a few days later.
That's true. Whenever my snakes have a sausage butt and I want to handle them I clean their tub. Usually by the next day they will have pooped and I can handle them without worrying about being crapped on.