Actually both the FAA and Transport Canada have recently come out saying they can not find actual information of 'ice bridging' be factual. The FAA and TC are now saying to activate the systems PRIOR to entering the conditions and to continue using the systems until one lands or exits the conditions.
And yes, I have for decades followed the old rule of wait.. no longer. NTSB now is saying as little as 1/4 in can increase stall speed 25-40kts.