I have only folded AA once or twice in limit.

3rd spade hit the turn, I checked, it was bet and raised back to me, I dumbed, they both had flushes.

Folded Aces once in a NL touranment, board paired the high card.

I folded KK or QQ in a HU SnG with no overcards on the board when the top card paired. I would have folded aces there too.