True, my statements shouldn't of been so absolute.
This is completely unnecessary with a Lycoming engine
Should be "This is generally not required in a Lycoming"
I have mostly operated the O-320, but also the 235, pretty much every flight in either the "serious icing - descent power" or "serious icing - any power" bands, but only had carb icing twice in flight, and one of those was in cloud. On both occasions the engine gave plenty of warning with rough running, and a noticable drop in performance, and selection of carb heat solved it in seconds.
RTN11, do you apply/cycle the carb heat as part of your pre-landing check-list regardless of whether you think you are in the "icing zone"
When flying for myself with in a PA28 with the O-320, before commencing the approach I check for carb ice. If none is found, and I am not in the serious icing any power band, I do not apply carb heat for the approach. This is in accordance with the POH.
Most schools I have taught at have the typical SOP to apply carb heat downwind, leave it hot for every approach and put to cold at 300'. This applies more to an older design of engine, or typically a continental and is not what the POH recommends for this aircraft type.
The reason for this SOP is that the schools think students are unable to think for themselves, and assess the real risk of carb ice, so they would rather have the carb heat hot for every approach. This does have some other affects, such as effectively enriching the mixture increasing the risk of spark plug fouling, something which I have experienced a lot more of on a Lycoming than I have ever encountered Carb Ice. As in the above post, the first thought was plug fouling, second was carb ice.