I know this sounds odd, but has anyone ever tried deliberately REDUCING population going into winter? Highly anecdotal, but last year I had a hive left with an open gap about .75" between deeps (don't ask why) for the first few freezes. I fixed that and insulated I guess early Jan., by which point there had been a ton of die off and I thought it was a goner. But in fact, that was my biggest producer this year as it seemed to get a jump on the others in the spring--it had good supply of stores left. (I don't feed any of my hives.) In the end, it seemed as if maybe the total die-off among hives had been the same but that this one had more earlier in the winter, preserving stores.
Made me wonder if this might be a strategery that could be usefully employed. I know it sounds slightly nuts.