The number of cums is determined by price you pay and summarized as such.
1 hr = 1 cum (all races)
2 hrs = 2 cums (all races)
2+1 hrs = 2 cums (all races except China and Malaysian)
3+1 hrs = 3 cums (China only)
6 hrs = 3 cums (Thailand, Indonesia, Laos, Vietnam, Philippine)
6 hrs = 4 cums (China)
What is important here is that you enjoy the sex. It is no point to have lousy sex and cum unlimited times. Please also remember that the girls are also human and should not be treated like sex objects.