I frequently have carb icing on an O200 in a Jodel. Usually I need carb heat immediately after startup. It's worse in the summer, in north Scotland, as predicted by the carb ice diagram. I use mixture lean along with carb heat in the air. It can sometimes be difficult to decide if roughness is due to rich mixture or carb ice. I don't see how cabin heat, off the right exhaust, can affect carb heat off the left exhaust. I was taught carb heat every 10 minutes. I've seldom had carb icing with the C152 or Pa28 161.
PS. DAR should have done the carb mice check before take off - most pilots think this is for carb ice only, but if carb miceing is present, the engine will stop on the ground.