I personally always book for one hour Sassy Ann. Purely because I can't see how it's possbile to relax into a 30 min appointment. I presume it's the financial aspect that makes punters book for 30 mins. I'm not made of money but prefer the hour long appointments - so it means less appointments than if I booked 30 minute ones. But it's time and money well spent.
Good suggestions above. I'm sure saying you have a another punter on the way will quickly shift anyone slow coach who is taking advantage of your time.
Moving to hour long appointments sounds like a good idea too, although you would probably be the best gauge of this.
However, there will always be chancers who seek to abuse a lady's time, and at the end of the day I think you need to forget manners and move them along by whatever means necessary. Manners need to be reciprocated. And when a punter seeks to stay on without paying for the extra time that in itself is a gross abuse of manners.
"Don't be reckless with other people’s hearts. Don't put up with people who are reckless with yours"