A reasonable departure time probably depends on whether the villa is booked the same day. If there are guests due to arrive the same day a cleaner will need a few hours to clean and launder the whole villa.
If there are no guests due in it may be possible for the clean to be done the following day.
I alaways say to my guests that they are welcome to have a late check out as long as there is no one arriving the same day. Maybe if you go back to the owners and finf out the situation regarding incoming guests.
Also if they are kind enough to ofer you a late checkout you could help out by getting most of the laundry done.