NEVER, EVER fold A-A preflop in a limit ring game. You have the best starting hand and are the preflop favorite no matter how many other players are in. In fact, you should want the betting capped because you will win more often then anyone else and the pots will be larger. Yes, your aces will get cracked more often with more players in, but that will be offset by the large pots you win when your aces hold up. If the betting isn't capped then you should keep raising. The only time it would be reasonable to fold A-A is in a tournament when other players are all-in against each other and the elimination of one will put you in the money or place you higher if you're already in the money. Extreme example: you're at the final table of a tournament and it's down to 3 players. You're the small stack and the other 2 players have huge stacks. You're in the BB with A-A. The button raises all in and the small blind calls. You should fold your aces here. Ideally the larger of the 2 big stacks will knock out the other player and you have just moved up to 2nd place money. Obviously the size of the stacks is a determining factor on whether to muck your aces or not. Back to the limit ring game. If you fold A-A preflop then you're invited to play at my table any day of the week.
