An SP once told me a guy came 7 times in an hour. :O
Personally my motto is if you pay for an hour, you should be able to get an hour... You shouldn't have to "hold" your ejaculationpleasure for a business techinicality. Obviously that guy i mentioned above the girl also told me he cim 2 times and the rest was "more traditional". I wouldn't expect an SP to allow cim 4 times in an hour or something like that and i supose if you want to pop multiple times in a condom bring your own so she don't pass a box on you lol. But seriously if you cum in the first 5 minutes and still manage to get hard fast and pop again at the 30 min mark, i don't think you should be denied more sex because you pop twice already..
But yeah your better to make sure its ok with her. Cost nothing to inquire. Explain that your a mister minute and you don't want to pay an hour for 15 mins of sex...