the older you are, the harder it all is
I'm always a bit sceptical about such claims which are trotted out rote fashion by UK military. Have there actually been any real studies into the subject? ADF accept aircrew applicants up to age 48 - it would be interesting to see what their experience is. Moreover, civ pilots often get type-rated onto completely new aircraft even in their fifties - and don't pretend a type-rating course is "easy"!