Preflop AA is the nuts, and of course never folding the nuts. There could be some really extreme tournament ICM situation or a situation like the
pokerstars "big game", where David Fishman wanted to lock up a win but was not allowed to leave until hand 150. But these are really the exceptions and only interesting from an academic point of view.
Postflop AA is just a hand. Sometimes we flop top set, and its the nuts, but most of the time AA is not the nuts postflop. So its just the same as any other non-nut hand. What is his range, what is my
equity against that range, do I have implied
odds or reverse implied odds, if I improve, etc.
In 100 BB cash game poker, I am typically rarely getting away from AA postflop in a 3-bet or 4-bet pot. But of course there will be exceptions like, when the flop comes QJT all spades, and I have two red aces.