There’s no rule. But I usually wear a watch. Prossie watches are unusual — the big hand seems determined to catch up with the little hand faster than mine. I often make a point of looking at mine and saying the time out loud followed by, ‘so we’ve got 30 until XX:xx’.
Sometimes they’re immovable. Another client booked in back to back; so it can be necessary to be very clear when the session started. Even so there’s the “time for coffee and a pie”. This is attempted by the prossie cheerily saying (10-15 mins before the end) “we’ve only got five minutes left”.
In such a situation, the gentlemanly thing to do of course, instead of yelling, “is it fuck!!
but to go autopilot and check your watch and say gently kindly, as if addressing a child with half a brain, “It’s ok, we’ve got 15 minutes actually”
(big smile). If she repeats the retard phrase, just say the correct estimation again in a sweet voice while eyeballing the cunt, watch extended kindly. At this point, she may claim your watch is wrong, and since you’ve left your Rolex at home she might just win: but at least you tried.