I think the best advice was given by hugh flung_dung and flying for fun.
Yes we are all agreed that followeing the POH is the way to teach and operate realistically. And we must ALL note and remember that most engine failures it seems are due fuel starvation or suspected carb ice. If one also adds into the equation the CAA safety sense info and that excellent chart on potential carb ice conditions, one will find that on nearly ANY occasion you are approaching in a Warrior or similar, that icing COULD/MAY exist.
By selecting carbheat just incase, you are covering your arse regarding what really happens in the real world (read the AAIB bulletins) and the CAA reasoning and advice. And by ensuring you deselect carb heat either on short final or on application of full power, you have respected the POH.
From my point of view, I would rather see somebody operating to the POH with an eye for "other" outside problems that exist. Remember, the POH is written to one extreme, and it takes the wise man to read between the lines and enter into the spirit of the POH and work with it.
Someone made the point here too that they didnt agree with one size fits all etc. Well that maybe true, but you have to consider that we are teaching/refering in most cases here to the SEP(L) Class Rating. We must give the student a firm and solid grounding to "get away with it" in any SEP (L) that they are legally allowed to fly. So sometimes, people teach these techniques that are not dangerous, or opposing the POH but if ingrained, will stop the poor sod from killing themselves in something far less forgiving...Such as the good old Continental engined Cessna's/Luscombe's and the like. There is simply not enough scope/time in the PPL to train for everysingle aircraft that can be flown within the rating priviledges.