I tried going to Cold on very short final - until I had severe carb ice on opening the throttle to turn after landing. I'm back to Hot until on the ground. In some conditions, I start the take-off run with Hot selected, and go to cold on the run. I've had carb ice stop the engine on a Konsin deiced runway on several occasions. (DR1050/O200 in Scotland.)
I seldom or never have touched carb heat in W. Colorado-Utah-Arizona.