This isn't an interesting topic, it's an absolute waste of time to discuss. Very rarely can you get your money in heads up with a 3-1 or better advantage, which is the case with aces. If they have a pair of kings you have more than a 4-1 advantage. It's absolutely silly to consider folding.
The only time folding can even be thought of is in a satellite situation, where you are nearly guaranteed a seat by folding, and calling puts your tournament on the line.