Bored and uninterested girls are a real problem.
Sounds fluffy, but my best experience is when the WG is really into the act and goes at it with enthusiasm.
I had one a few years ago who was a real dirty girl and a total nymphomaniac. She would undress at speed when we met, and would pull my dick straight into her, no foreplay, no shower or clean up, just 'speed shagging' and she would have violent and very wet orgasms with lots of noise.
It was like a rodeo!
Never ever had an erection problem with her and I could squirt in a few seconds with round two in similar fashion about 40 minutes later.
Enthusiasm wins hands down.