Another thing I've noticed, and yet another possible friend, is that battery life of mirrorless is even more affected by cold temps. I know many on this forum
live in balmy areas (Gene, David) but up here in the mountains doing (trying) to do astro I've learned to embrace those chemical heat packs (you know the kind that
you can put in your boot, some shaped like your foot with stick to hold it on the sock). I even wrap my lens esp. near the hood area with them, then use a slap cozy to
hold them in place to prevent condensation.
So for battery life when its seriously cold I stick one on the bottom of the battery grip.
I'll even keep a smaller heat packet in a pocket where the extra batteries go 