I agree with Steve, in addition I advise that I am unable to confirm late check out or late luggage leaving until only 24 hour beforehand. If they want to guarantee holding their belongings then they will need to pay a fee (around 50% of a nightly rate). I do advise of alternative places to store their luggge.
I used to play it by ear but recently have found people taking advantage, and yes, most do use the toilet, have a glass of water, re-arrange luggage and if the cleaner has been or if I have cleaned, then some things need to be re-done.
Ive also had someone return to 'pick up their luggage' and my cleaner was there turning over the apartment, not only did they turn up with 4 other people (non of which were in the booking) she was on her phone for around 30-40 minutes. When my cleaner advised 1 hour after the 6pm agreed extra check out, she had dinner reservations, she said she wanted to heat up and eat some pasta from the fridge before her flight. My cleaner advised no she needed to leave and she needed to take the keys. Upon being told this, she then called me. I suggested she reheat her meal, and put it in a take away container. She advised there were none, when I said she could have one of my storage containers she did not like the look of them. She was quite a self entitled guest, I then put my foot down and said I had been more than generous with a late check out even later than agreed (I was at that time well aware of the extra people who came over). And advised she would need to leave and my cleaner needed the keys.
Sometimes people if given extra courtesys then want more and more.
I find asking arrival and departure times including flight details BEFORE accepting a reservation goes a long way and again, communicating mulitple times before, during and 24 hours before check out what your expectations are.
Good luck, let us know how you go!