In the Military, you are (90% of the time) an Officer before you are a pilot. Maybe that's why it can't go Civvy - Mil ?
Military pilots may/may not be the best (thats up to you), but before they could even get to the stage of flying, they were stripped down and rebuilt as military personnel. It's my belief (from various family and friends who are seving and ex-mil) that once you come round to the military way of life, you're stuck there.
To go Mil - Civvy, you have the flying skills but a different attitude, a more 'tactical' way of thinking (for want of a better word) than your civilian counterparts.
To go Civvy - Mil, not only will you have to be retrained flying-wise to calculate quicker, react faster, learn new terminology etc for the cockpit, you need to learn a new way of life, become a new person entirely and recognise that you no longer represent your airline, but your country and those around you.
Pilots are elite be they civilian or military, if you're lucky enough to become one then you appreciate the hard work involved. Each have their own ups, downs, positives and negatives, but at the end of the day you're all in the same fold (ish).
To sum up my ramblings, the military demand you change your persona, civilians do not, hence why changing an ex-civ at 25-40 will be so much harder than vice versa. Ontop of that i'd rather have a pilot who thinks more 'outside the box' that by the book all the time. I'd trust military guys more than civilians in a stressful situation purely from their military training.
Hope that makes sense...
