this is only my 7th post..... so no-one will knowme but i thought i'd put my 2p worth.
i always use carb heat from the moment i drop the power to start my desent (and take 2 stages of flap).... i leave it on until i touch down.... in the case of a touch and go. Get rid of all my flap , carb heat off then full power and rotate at desired airspeed. and for a go around, full power, carb heat off, drag flap away pos rate of climb 2nd stage away, pos rate of climb 1st stage away.
as for carb heat on my downwind checks, its the first thing i do and the last thng i do.... so it stays on for my entire check. as you say.... too much is better than too little.
PUT - Stapleford in Essex