I'm not near my library to look up the exact reference, but Nevil Shute writes in "Slide Rule" about employing a small company Chief Pilot - this was in the 1930s I think.
They got through a small succession of young, bright, capable - but generally unreliable pilots with too much interest in the lifestyle, and too little in the responsibilities of the job.
They eventually employed a chap in his mid 40s, mortgage, children, perhaps less obvious ability than the youngsters - but they never looked back. Utterly reliable, always had an eye on what was good for the company, was with them for many years and never ever let them down.
His moral was to always try and employ somebody with a lot to lose if the job goes wrong.
Personally, whilst not in the airlines, I work and employ a fair number of people in aviation. I'm most conscious of (a) getting the right people regardless of age, and (b) trying to maintain a reasonable age and ability gradient across the organisation so that everybody can see a career progression and learn from the different perspectives of others - that might depending upon circumstance have me most interested in employing youngsters or oldies, but I'd never put a hard and fast rule on it.
G