All the variables you mentioned come into play. Generally speaking, there are a couple of rules I go by when I play. If 3 of my suit are out, I generally won't play. If it going to be heads up a flush draw isn't worth it.

In the case you mentioned, I would def. call 4th street. There is a lot of action and you have an overcard (unless another ace raised).

You want to play flush draws---
A)in a multi way pot
B)when your cards are live
C)when you have overcards
D)when it is cheap to get in

from there you can mix and match to see if you want to call 3rd or 4th street.

example: Well, I didn't hit a diamond on 4th, but it is 6 way action and only two diamonds are dead. call

example: wow, four diamonds are dead, but I have (AdKd)6d5h and there is a Q betting. Since I have two overcards, I can call here.

example: there is 4 way action on the turn, I missed and have little cards, but all the diamonds are live. I can call.

example: I have (Ks Js)4s 2h two spades are dead, an ace raised and another ace is suited (XX)AdQd even if I make a spade or pair, I am likely to lose anyway. Fold.

example: an ace raised, and I called with a live flush. unfortunely, it ended up heads up. I made a fourth of my suit, and he matched his ace and bet double. (6d4d)8dKd vs. (XX)AA unless you know this player is unlikely to have aces, fold. even if he has a pocket pair you are a 3-2 dog.

example: it was 7 way action, but 4 of my suit are dead, and I have nothing else. fold

If you always mucked three small cards when you miss on fourth, it wouldn't be a bad strategy.


Good luck