Do SPs enjoy...?
I like a steak, but I wouldn't enjoy 5 steaks a day, 7 days a week in the same way, even if I was served the greatest, tastiest steak ever know to man, in the best restaurant in the world I'm probably not really going to "enjoy" it in the same way as the bloke on the next table who only has a fairly ordinary steak once a month. There's no point in comparing an SPs attitude towards sex to our own.
The reason many advertise over 30s only, is as previously stated, the punters tend to be over enthusiastic, and also they are often more unreliable