My counsellor charges per hour. However, our session is 50 minutes and the other 10 minutes are for her to write up her notes. It would never have occurred to me to insist on the full hour, so I have no idea why some men think they're going to spend all 60 minutes of a one hour session going at it.
The whole 'clock watching' thing is only something I have come across when I briefly used AW. It's not something I have encountered anywhere else. I found a few men asked me about this and all wanted to book initially for an hour and to see how things went. I always declined to see them as I suspected they would push me to stay for as long as possible for an hour's fee. For me, anyone asking about clock-watching have screened themselves out.
I only do outcalls, so am a little slack with timings and do sometimes over stay by 30 minutes or so. But then my outcalls are usually 3-4 hours at a minimum anyway, and am well remunerated for this, so an extra 30 minutes is fine. Even so, should I find myself staying an extra hour, I expect to be paid, and am very clear about this.