Some not so well reviewed ladies will only go for one pop, and some clients can only get off once in the hour (if that in many cases).
So, time, the lady, the client, the circumstances and more all have impact on the number of pops... while it may be considered nice to get off more than once, I have had many sessions where only one was achieved, but that was one hell of an O.
Personally, I prefer "quality" over quantity....

In my experiences, in most cases a provider will allow the gentleman as many pops as he can achieve during the alloted time. But be wary of the time..if you engage in 10-15 minutes of get to know you conversation, and then 35 minutes of fun, you may only have 10-15 minutes left for round two. In this case, a second pop, due to time constraints, may not be feasible. Now if you want two pops in the hour, you may have to move things along at a much quicker pace so you have time to recover in between rounds. Of course there are some providers who only allow one pop in a session, period (even if you have 30 minutes left). If you can know the rules ahead of time, it helps. Booking two hours or more will almost certainly afford you the opportunity for multiple pops.

At some point, once business is taken care of, she will ask you "what do you want to do?"  At this point tell her that you are hoping for two rounds.  If she is not up for it, you can pace yourself to maximize the hour.  If she is up for it, she can help pace you to achive your desire.

Yes, a longer appointment does facilitate multiple pops, but in my experience, two, and a couple of times three have occured in hour.

One of my "local" favorites is married and her deal with her husband is that she will only allow one pop per hour paid for.  She also has to promise him not to do CG, as it gives her an awesome O.  Last session she "cheated" on him and rode the baloney pony.  I was worried the neighbors were going to call the cops, she yelled so loud