My girlfriend is 5'11" (and taller than me, and a model, dancer, etc etc) and yes it is a bit hard to reach standing, but I figure that's a common human experience. Sitting down and such you don't even notice.

I haven't asked if the concept of needing an even taller guy has ever occurred to her, but the even stranger one of either of us caring if she's wearing heels sure hasn't come up.