In my experience, I have encountered roughly three levels/tiers of service when it comes to "SOG per hour" policies, and the distinctions between them are partially a function of price range.
1) "One and done." These providers will give you only one cup in a one hour session. I don't know how they would extrapolate that policy to longer sessions, because I would knowingly never waste my time and money on such a meager level of service. Most of them will at least honor the full hour of time and provide some other kind of service after you pop (cuddling, massage, etc.), but some of them will give you the signal to leave after your one and only pop, regardless of how much time you have left.
2) Two pops per hour. This seems to be standard among providers who charge up to or less than $300hr in my major metropolitan area. In fact, some of these providers seem to equate "1 hour session" with "two pops" and will give you the cue to prepare to leave after your second pop, even if you still have a significant amount of time left on the clock. I have only encountered one $350 per hour provider who had a two pops per hour limit, which I have found to be unusual in that price range (and, IMHO, totally unacceptable at such a high rate).
3) Unlimited pops per hour. They will give you as many pops as you want and can manage. These providers usually start at $300-$350 per hour in my major metropolitan area. The only exception to that price floor that I have ever encountered is a $200 per hour BBW provider who gives three BBBJCIM pops per hour - her rates are probably lower because she is a BBW.
I am still relatively young, so 2 or 3 pops per hour is normal for me. I would normally consider only one pop per hour a disappointment and would never knowingly book a session with a "one and done" provider. Two pops per hour is my typical rate, especially if both rounds are CFS or CCBJ. I can usually do three per hour if at least one of those three rounds is BBBJ. I never do sessions longer than 1 hour, so I do not know how my rate would extrapolate into a longer session.
My personal record in a 1 hour session is four pops - all of them were BBBJ pops from a provider with a powerful oral fixation who must have been sucking my cock for 45-50 minutes of the whole hour and charged $300 per hour. I have also had two or three other providers in the $350-$400 per hour range try unsuccessfully for a fourth pop in a 1 hour session.