I haven’t noticed much of a difference between our lavs and any other carrier. Sure there’s going to be pee sprinkles on the floor after a 4 hour transcon but that’s not unique to Spirit.
Last I checked the cleaners still run on between every flight and clean the lavs and the rest of the plane just like almost every other major airline. Next time you run into a JetBlue pilot ask him/her who cleans their planes between flights…