Here is my opinion and perception.
It really does depend on the individual provider what the answer is, on the break point between High and Low Volume. If a lady is in charge of her own destiny (i.e. truly independent), she has control of the volume knob.
Some successful ladies will only take one appt a day and charge alot or have that one appt all day.
Some unsuccessful ladies only see one a day, cause that is all the bookings she can get. Not hating, just stating facts.
Some Ladies have a goal in mind and see a certain amount of guys a day (if their dance card is full).
The average seems to be about 3 or 4, from ladies that I have polled.
Now on the High end of the graph are popular ladies that work for agencies and are booked morning to night with 8 or more appts. That is why some really popular agency girls leave early after a few days, with a sore pussy but cash in hand.
Everything in moderation. As long as a lady provides good service, you should not be concerned about volume. Many guys like to see a visiting girl early in her schedule hoping she will provide better service the first or second day, as apposed to the last day of her schedule, when she might be burnt out (if High Volume and popular).