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Imo it is an age thing as well.
Younger=hardier. There is obviously a point where it is too cold for anyone but the younger you are the better you handle it.
I just look at my kids getting around...

I can remember always being cold wet and miserable as a grunt when on ex in NZ.
Waiouru and Tekepo humping around half your body weight in rain, hail, snow or shine. Digging in, in frozen ground...