I can only speak for Euphoria and Vogue - I don't find this to be an issue with them. When James is booking, I know he slots 15 minutes between appointments to give the girl some buffer. And if they're late, it's on them, no loss of time to me. Vogue may be late arriving, which is normal for an outcall agency because of traffic, weather, other pickups, etc. - but Franky and Celina have always been great about making sure clients get their full time. A non-issue for those agencies. Which is the right thing to do.
With showers before and after, it's always worked out to be a 45-50 minute experience. Depending on the SP - I've gone over sometimes because we both lose track of time. I've never had a booker chew me out for 5-10 minutes over (including the shower / clean-up time). Back in the old days, when girls' schedules weren't so packed, you could actually call the booker with 10-15 minutes to go, and extend the session another half hour or hour. xxxtase, Vogue, Wildtimes... Can't imagine that ever happening now. And with SPs you knew well, especially with outcalls previously, 15-30 minutes over time would never be a problem. The number of hours with Zoe where an hour wasn't an exact hour... Again, can't imagine that happening now.
And these days, to be honest, if there's little connection / no kissing / unattractive face / no DATY / etc., I don't really want to spend the full hour. Once I get off, the job's done. For most of these girls the last 2 years in Montreal, I'm more than happy to leave with 15 minutes to go, or for them to leave my hotel room, just so I don't waste any of MY time.
Realistically, unless you're on the blues, I can't imagine having FS for more than 15-20 minutes. More likely 10-15 minutes at best. Which is why FKK's make a lot of sense for me at the moment. 30-40 minutes of real action is more than enough time. And you can chat up an SP on their time in the lounge, if that tickles your fancy.