The condition people experience is not the condition after cleaning
A washroom cleaned thoroughly at seven in the evening is excellent at eight the next morning and variable by mid-afternoon. Nothing about the clean was inadequate. The condition that generates complaints is the one at two o'clock, and that is determined by usage volume, consumable stocking and whether anyone attends during the day. A scope addressing only the overnight service is answering a different question from the one occupants are asking.
The practical response is usually a short daytime attendance rather than a longer night shift, sized to the building's actual pattern. In a premises with a lunchtime peak, a check after that peak does far more for perceived cleanliness than an extra half hour at night. Establishing the pattern is a walkthrough exercise, and it is worth revisiting after the first few months because the initial estimate is rarely exactly right and both parties learn from the complaints that do arrive.
