We always book aisle and window in E+ and keep them - I'm 6' and prefer an aisle to be able to get out easily; my SO is a nervous flyer and prefers the window to be able to see the ground at all times (I don't question, I'm just reporting the news... ). If someone is assigned the middle they frequently "offer" to switch so we can sit together. Needless to say they are uniformly disappointed when we decline.

It's interesting to me the number of you who will switch so that one of you is in the middle; for us we each have our preferred location.