Kgirls I know occasionally have a day now and then with the kind of volume you suggest, but this is most often a manufactured rumor associated with sex slavery (mostly Mexican, but occasionally Chinese) and has nothing to do with Kgirls.   Anything more than 6 customers a day is not sustainable over the long term, and this is why the top tier girls limit themselves to 4-6 customers a day.  

 
I have known a handful of girls that tried to keep up a 9-10 customer level (which included a couple that were only 30 minutes) for a full 6-day week, and they all three wound up on an IV drip in the hospital for the next 48 hours with life-threatening dehydration.  (I visited two of them on different occasions when they texted me from the hospital.  A talk with the doctor told me how serious it was).    

 
Most girls will wait a few hours in the morning to early afternoon to see how the schedule is shaping up for the day and then tell the booker how many more, if any, he can book for that day.  I have had a few regulars over the years that would text me screen shots of their bookings on the scheduling app to show me where the gaps were in case I wanted to book on short notice, so I would know what time to request from the booker.  In the current climate of many girls using multiple bookers, the schedule can fill up rather quickly, so no one should be surprised on any given day that a girl has a full schedule my mid-morning.  If it's a girl you are a regular with, then I recommend that you text her directly and if you are considering seeing her that day and ask her what the best time to request is, IF you have some flexibility of your own.