Agreed. And in deep cold, several thin fleece balaclavas, matched with several mid-weight fleece toques. Mix and match as needed; and have one set drying (if possible) while you wear the others.

Staying warm is not really about insulation; moisture management is the really big deal. Multiple layers make it easier to adjust to the conditions, and dry things out on the fly.

Outer layers will often have an impressive layer of frost from the moisture that's been pushed out. Whip that off and your headgear is almost halfway dry.

Mitts are ideal for warmth, but they're too darn clumsy for most tasks. I often shove gloves inside a mitt-style outer shell. A practical compromise, mostly. Currently, I'm messin' with some very dextrous neoprene ice fishing gloves; wonder what outer shell would suit them.

[BTW, tonight's forecast: -33C. Over the next couple of days, theory and practice will have a chance to compare notes.]