Since switching to newspaper I clean as soon as anyone is dirty. Sometimes it's just one or two tubs, sometimes almost everyone is dirty but I typically end up cleaning daily or almost daily.
If it's just a fairly dry mess that doesn't soak through the paper I may just change the paper but if there's any moisture I wipe dry with a paper towel, soak in F10, wipe out and replace newspaper. Unless anyone has gotten anything icky in their water I usually only scrub out and disinfect water dishes once a week, and just ensure they're filled the rest of the week.