If they are more than 15 min late, I tell them they can have another appointment, but will still have to pay. They can choose to get another treatment, eg. manicure at the current appointment, so they will still have gotten something for their money (they can choose whatever treatment there's time for, and that costs less or the same...) My 15 minute limit is on every treatment over 1 hour, if it's 1/2 an hour treatment, then 5 minutes, that's the time I can cut if I really hurry and don't speak at all LOL
It's so annoying...even if you are not having clients after (or in your casew have to go out) it's just not acceptable...