The old bones start to ache with cold and even more so if it is humid and cold. Then there is the snow and ice > walking is harder and falls usually result in broken bones.

There was only 16 squadrons of RAF fighters that used 100 octane during the BoB.
The Fw190A could not fly with the outer cannon removed.
There was no Fw190A-8s flying with the JGs in 1945.