Ok, maybe I'm totally off in this category, but I've found that women who've slept with jerks in their past tend to cum a lot more. Well, that was constructive.

Anyway, sometimes it just takes a few trys if you're willing to work at it. I wouldn't advise waiting as some people say. I think people should open their body up to experience when its ready. If your happy and he's happy, go for it. It gives you more time to learn about what eachother likes in bed and what are your turnons and turnoffs.