I remember reading some piece of BP cannon, which said that GTVA veteran pilots often stayed in the military as leaders or flight instructors for future pilots.
From memory, this applies more to the situation close to the punch up between the UEF and GTVA; they found the Fighter Corps on experienced operators, rotating pilots after a tour of duty in a frontline squadron to the rear in order to train new pilots. So as the UEF's Fighter Corp, which actually is founded around experienced operators, starts to decline as the very experienced guys stay at the front until they die (nowhere to rotate them to, really, nor is it a feasible option), the GTVA's pilot quality steadily rises, as the sink or swim situation leaves only those who can hack it, and their knowledge and skillsets which are passed on to nuggets/bograts/whateverthey'recalledinyourregion before they move onto places in fighter squadrons.
In fact, we discussed 'POCT: Post Operational Conversion Training', in BP:Tev, where newer pilots are trained by veterans who run several exercises and lessons of their own in order to impart their knowledge in a solution that's far easier to implement that rewriting the entire line of the sausage factory/pilot training regime.
Moving them up to somekind of warship or tactical officership might make them less effective given their backgrounds as pilots.
This is quite a likely conclusion to draw. When the GTVA promotes pilots out of squadrons to executive and admin positions, their squadrons are no longer formed around experienced pilots who fought the Shivans, and have lessons to pass down.
And you have pilots who genuinely love flying and have few aspirations for executive careers are known to dodge promotions left, right, and centre in order to stay flying.