a wrote:
If you are running at low manifold pressures you have set up a
condition for carb icing, haven't you? I'd suggest it would be prudent
when landing to keep the carb heat on until touchdown, or until you
decide to go around. As has been pointed out here, carb heat and
throttle can be operated with one hand when advancing the throttle.
Why take the chance of growing some ice just when a deer runs on the
runway 500 feet in front of you while you're in the flare? Or, more
likely, someone has finished their run up and is taxiing out when
you're on short final? You have the carb heat on as insurance you'll
get power when you need it, don't cancel the policy prematurely.

Keep in mind this is written by someone who flies an injected engine!

How fast does carb ice form? If you've had carb heat on from abeam the
numbers in the downwind, is ice going to form from short final to flare?
I usually leave mine on to touchdown, but a CFI-friend shuts off carb
heat when on short short-final in anticipation of a possible go-round.

Keep in mind this is written by someone who flies in Arizona!