This is only my own viewpoint so of very limited helpfulness.
I find the best punting policy is to punt less frequently and allow the chance to save up a bit between punts, so that I can have a punt of 1 hour, or if the lady's rate is on the expensive side then 3/4 of an hour. I find that in general that gets me a much better quality punt as it gives me and the lady unrushed time to get into the punt and enjoy it.
Personally I find a 30 min punt can be rather 'emotionless' and rushed particularly if the lady is a first time punt. As for a 15 min 'splash & dash' I fail to see personally how that can lead to any satisfaction at all. Unless a punter just has the sudden urge to visit some munter whose hygiene is lacking just for the sake of exploding over a pair of big, saggy, spotty tits. In my mind that is just sordid.
In fact I wonder percentage stats wise just how many 15 min 'splash & dash' punts actually resulted in a positive review. Most likely not mentioned owing to the embarrassed punter preferring rather to keep the sordid experience low key.