There is no single empty window
A schedule assuming an empty floor at six will collide with a practitioner seeing a last appointment at seven thirty. The cleaner then works around occupied rooms, defers them, or waits, and none of those were priced. Ask each provider what they assume about occupancy and check that assumption against how the floor actually operates on a normal week and the resulting schedule is rewritten informally by whoever is on site.
Get the real pattern from the occupiers rather than the building manager. Suites vary, evening sessions move, and the published hours often understate how late people are actually present. Half an hour asking two or three occupiers before quotes go out will produce a more accurate picture than any amount of discussion after the arrangement has started and it costs nothing beyond a few short conversations in advance.
