Good point Debk. I agree there is a limit to the time available on a back to back changeover (which is most of them), to deal with these things and that an extra charge for a particularly time consuming job is useful as a deterrent. Worth thinking about doing that!
However, using your system, if Stephen's guests cleaned his oven immaculately, but left something else in a state that took just as long to clean, he could not be reimbursed because he'd only singled out the oven for a possible extra charge. Whereas under our system, the amount of cleaning we include in the rent is agreed in terms of hours it takes in total, not by any particular aspect. So my point was that cleaning a cooker and wood burner would be regarded as part of that normal clean for Stephen's house, and therefore ought not to be charged as an extra if left in a normal state after normal use. If the oven AND everything else were left in a very messy state, then an excess cleaning charge could be made on the basis of hours, regardless of which appliance it may be that has tipped the scales.
Certainly worth reviewing at regular intervals to see where improvements could be made, but I still think everyone's best interests are pretty well covered by the clause I shared above.
Useful thread, thanks for posting Stephen...