With me there really isn't a norm, sometimes I can go on a punt and I just can't manage to pop at all! Even if the girl has been really hot.
I don't know whether chemistry comes into the equation. It could possibly be how I'm feeling on the day of the punt.
It could be that the girl just doesn't float my boat, or I may be tired so that could affect things.
Alternately I've been with WGs who may not be as fit/hot.
But with some I've found them to be a real turn on in other ways, nice personality, passionate, great at FK, and easy to get along with, and don't try rushing me in any way.
Bit of a conundrum really.