I would essentially never c-bet on a board w/ 3 overs. I wouldn't even consider it. I would c-bet only occasionally if there are 1 or 2 overs. Of course your c-bets depend on what's going on. Like whether you are heads up and position.

Almost never c-bet with 2 or more overs.
Occasionally c-bet with only 1 over heads up.
If your c-bet is called almost always give it up unless a scare card hits the turn and gives you an opportunity to bluff.