I would fold AA preflop only in a satellite situation where I am guaranteed a seat if I fold, but calling off with AA would only yield an 80% chance to win (rather than 100%)
As for postflop, there are so many things to consider, how deep are stacks, what
hands are in our opponents range, how likely he is to have improved.
Against very nitty opponents I can find the fold with AA. The main question to ask if 'would my opponent be playing like this with just one pair?' and that comes down to their tendencies as well as how much money they are putting in the pot.
Also remember, playing a defensive showdown strategy is always an option too. There's no rule that says you can't go into check call mode with AA on say a JT9 board. And against certain players if it gets too expensive, it can become a fold later. I really try to feel out the strength of my opponent based on their style of play and betting throughout the hand, tends to work out pretty well!