I was pretty clear that this is from my perspective, from ample experience.
you said 'The time starts when she returns to the room after handing over the cash.'
if you have prefaced this 'in my experience,' or 'I think generally' it would have have read that this was your perspective
but you didnt, you put it in bold, and then said 'I have done this for several hundreds of punts'
you stated it as a fact and that your opinion is worth more than others.
its an opinion, plenty of other is the site with similar experience to you, you are not a special and unique snowflake
Although in your same post you illustrate some of the disadvantages with your approach.
it is not my approach, I dont get to decide when the appointment starts and ends. neither do you. the girl does
she might be cutting your time short, you may argue, but if she says your time is up - you have to leave.