Sure...I'm aware of the statistics. And when you are talking about stroking to climax, your point is relevant. But when talking about a couple having sex to mutual satisfaction, the stroking isn't all there is to it.
And that, I suspect, is the problem with this couple. So far, the only sex I've seen from them is Artur stroking to achieve HIS satisfaction. I haven't seen any action from him directed toward Elena getting anything out of it.
Who knows...maybe Elena wants it like that. Maybe she doesn't want sex, but because she loves Artur she''ll let him have what he wants...a good squirt. Or maybe she has never, ever, had good sex and thinks this is what it's all about.
Now, for me personally, a half hour usually isn't long enough. But then, I pay attention to my Lady.