<<which can't be easy to change at short notice>>
But the shift pattern I worked in NATS was a regular 6 on, 4 off for 25+ years so could be forecast as far ahead as was necessary, not that I am a pilot!
A number of my working colleagues worked as commercial pilots, flying on their days off and even before or after work on the same day. I sometimes wondered how much family life they had, if at all!