c/f on this turn seems absurd to me.

What flushes are we putting villain on that won't raise the flop at least some percent of time?
AJss/AQss are the most likely FD's and are both combo draws that will conceivably raise flop a good percentage of the time.

If villain is showing up with things like A5s etc, then he's probably also calling JTs, KJ/KQ etc.

If I'm checking this turn it's with the intention of c/c, to protect against all the other times I'm c/f stuff like AJ/AQ.