When I show then it is for reasons other than playing optimal poker (ego, in yo face, etc).
Just last night a guy at the table showed a J3 bluff that he bet huge (totally missed the flop). Ran everyone off and scooped the pot.
Later on another huge bet (all in) - I called with TP - he had J5, which again had totally missed the flop. I am not calling that had he not shown earlier.
Side note: I think I would much rather have them wondering if I am on a heater and hitting everything than wondering, "Is he bluffing, AGAIN? Cause I know he bluffs and this could be one of those times. Maybe I better take some time to really think through the action of this hand."