Age is both relevant and relative: When you're 16, a year or two is a significant, and real, obstacle; by the time you're 20, a couple years often doesn't matter; and when you're 25, 5 years (or more) needn't be a problem. In general, the younger person in a relationship is more vulnerable to emotional and psychological damage while the older risks social prejudice and punishment.

As for height - men average a few inches taller than women, so it's commonplace for the guy to be taller and this seems to have been socialized into an expectation. Nevertheless, I (at 6'2"; 188cm) feel uncomfortable with people more than 6 or 8 inches shorter. I've often wondered what it would be like to have a relationship with a woman of my height, or even taller . . .