Not in aviation but worked shifts most of my life and a fare few were 12 hr shifts.On my last job and I was 72 (I liked my work) I succumbed to an illness (pericarditis)due to fatigue and a week of rain !I Got very tired and finally started having chest pains and that was that,company said goodbye don't come back!So I guess I was just too old for shifts and work told me!!