Just to add my two cents.
I thing the time set should respected on both sides. Half hour, hour, 45 min whatever. You're paying for time.
Having said that i have found some ladies using the "do you want to take a shower?" as a ploy to reduce the amount of time. So i take a shower before i see the lady and reply "no I just took one, thank you."
I have also found - more in the massage industry - that the clock in the room is 5 to 10 minutes ahead of mine. So I confirm the time when I arrive.
lets all be respectful of people's time