[RoundTower]

I disagree with almost everything pete wrote, that he can expect you to have AA more often than the nut flush based on your flop action. I don't think you should always bet/3bet the flop with AA here, and I certainly don't like it if you don't tend to play the nut flush equally fast. Also, there are way more combos of Kcxc than of AAxx, and an aggressive player is opening most of them on the button. Also, AA is more likely to take a free card on the turn.

I think it's a clear call. You are priced in or very close if he always has a flush, so if he ever has less it becomes a must call.