Rose and the Doctor are still shagging like mad, though Jack has long since fallen by the wayside, deflated. Male biology hasn't changed that much over three millennia.

Time Lords, it seems, have a much shorter refractory period, and women have never had that trouble at all. The two of them could probably go at it all night without ever having to stop.

For a moment, he wishes that he could be granted unlimited life, unlimited stamina, just so that he could keep up with his partners. But then he dismisses the thought, and settles back to enjoy the view.