http://www.lycoming.com/support/publ...fs/SI1148C.pdf
In the case that full power needs to be applied under these conditions, as for an aborted landing, return the carburetor heat to “Full Cold” after full power application.
Lycoming, at least, are pretty clear on their use of carb heat. If you use it on the approach, it should only be selected cold after full power has been selected for a go around. Other than that, it can be selected cold once on the ground.
The whole putting it cold at 3-500' is a UK flying school nonesense and can simply act as a distraction at a rather critical phase of flight. The only exeption I would include is landing on rough grass when you wouldn't want unfiltered air going into the carb, so would select cold as soon as practical.