[cero_z]

"of course if you dont get a fourflush then you probably should be out of there even if you pair a card, if you will still take a lot of heat."
This is completely wrong. What you have is a premium hand for the game you're in, so you don't mind putting in a ton of bets on 3rd street, and on 4th street, even if the card you catch doesn't help you at all. The only times you can consider folding on 4th are: When your cards fall very dead (like if 4 or 5 spades and some straight cards land elsewhere), or when someone pairs their doorcard and you are almost sure they have trips. This second event will not happen much in a game like you describe, meaning that you won't be sure someone has trips because they're raising with so many hands on 3rd street. These hands can be frustrating, as you usually go all the way to the end with them, miss many more than you hit, and spend a lot each time. But the pot will be enormous when you do hit, which will easily compensate for those other times.