Interesting stuff carb ice !! When I picked up my Auster from Redcliffe it was really bad on icing. Had to use carby heat quite extensively including on reduction of power at top of climb - quite a warm environment but high humidity. Here at Camden it very rarely needs to be used at all - although per normal practice I always have it on hot while descending and prior to landing. I have also had quite a few instances of it in an old Piper Cherokee 180 I fly. Some are worse than others.