Interesting: I've never really been a big fan of hand-jobs from someone else. I guess the thing is though that the hand can grip you much more tightly than the vagina can, and the owner has more control over what it does.
You could ask your wife to consciously squeeze your cock with her pussy when you're coming (feels fantastic). When you're thrusting before you come, ask her to squeeze when you're heading out and relax when you're heading in *sets up a nice complementary rhythm and makes it feel as if she doesn't want you pulling out. Also, try different positions: some feel tighter than others, as you know.