Smudge
There was a document called Group Air Staff Orders which covered the length of crew duty days and the minimum crew rest times for sustained operations. They could only be exceeded with express permission from Group (or FATCOCK as you prefer to call them) There are exigencies for wartime considerations of course. The secret is when to push on and when not to. You don't get brownie points for causing a disaster through crew fatigue.
Like our lady eng in Darwin. The captain didn't want her to go sick. I told her to do just that. You need three for a mutiny.
I try not to make decisions anymore.