I'm with Borko on this one.. if you don't like the way the customers use the service you offer.. fix it so it works for you by either getting rid of it, putting very specific terms on it and stating them clearly (no 2nd shower or no extensions on time, perhaps), or only offering it to clients you have already seen that you are sure would be the kind of appointment you find ideal for that kind of thing.
Running a business independently is a lot of responsibility, but one of the major benefits of being your own boss is never having to do anything that you find silly, ineffective, or pointless thanks to company policy written by a jackass that can't even imagine actually doing your job but still dictates exactly how you ought to be doing it.