I am the complete opposite OP, kissing and sex at the same time makes me finish faster, which is sometimes too fast.
You've got that the wrong way round mate, the quicker you cum the better for the SP, less work for her, especially those who have a cum once policy.
This would depend on the SP's business model.
If their goal is to turn a 30 minute booking into a 10 minute booking (for whatever reason) then great.
If their goal is to turn a 30 minute booking into a 2nd 30 minute booking into a 3rd 30 minute booking and so on, then they may be looking to maximise punter enjoyment.
So, if a repeat custom focused SP could work out that the OP wanted more kissing to last longer during sex, they would provide that. I am not sure they would realise this, but they may just naturally combine kissing and sex as part of trying to give a good service.