I think some of it must have to do with setting up shots as well. I agree that overly long jerking is pretty much of a turnoff. I do like it when the girls jerk off the guys. I know i prefer it in my own life.
It just creeps me out to see a guy jacking off over a girl. Looks so fabricated and exploitative. Particularly when Peter North does it. It turns my stomach. That's why I love your site, Chica. It has a certain erotic realism about it. One can see you guys love each other.