to which you will never get 100 percent correct answer. For many ladies volume goes up and down depending on whether or not they are at their home base or on tour.
These days I stay in NYC area 2/3 of the month. This means that I usually see 2- 4 people a week since I do have to attend to my real life obligations. Remaining 8 - 10 days a month I travel. Some of these travels are for 12 - 36h dates and some are tours.
Guess what? When it comes to touring, seeing less than 3 - 4 people a day means you lose money. A LOT of it. Any girl that says different is full of it. Nobody is going to spend 2k on traveling to another city and see one person a day. if the do, it means they are either charging enough per hour to make profit or seeing enough people to make profit. Longer dates are not exactly "easy" either. A provider may be seeing only one patron for 2 days but that means she is ON for entire time.
All that said, if a girl is seeing just couple of people a week and one week she suddenly gets 10 requests, she is going to take all 10 appointments. If a girl just did an overnight and was going to take a day off but got request for another, she is going to take it. Doing otherwise would be dumb since in this business you never know when the next "dry spell" is going to happen.
Does volume have any correlation to quality of service? To a certain degree. In addition to purely physical aspect of it, there is such thing as emotional burn out. Some girls know how to make sure they maintain healthy normal lifestyle outside of this business others get in too fast and too deep. Like everything else in life it comes down to the person's individual characteristics and abilities.