Hours have little relevance. I could easily do 30 heavy-jet hours in four days and be fine. However, do it with time-zone buggeration and you are knackered. IMO, the real issue was fleet workload. Some fleets would get completely overworked while others went gardening. No GASO's broken!

43 hours per month? Whether in a Phantom or a F3, that must have involved a fair few of the around-the-entire-UK-with-big-tanks TACAN crawls which it was rumoured the AD fleet periodically undertook in order to balance out the 30-minute ACT trips...