I worked for an airline who had an F/O in his early fifties. Thousands of hours in his logbook and several type ratings. He was so keen he even paid for type ratings on different aircraft out of his own money.
Top bloke. Commander? Not as long as he has a hole in the front of his face to stuff food in. Age and experience are not the only criterea here.
Same airline made a Commander a Training Captain as soon as he had the requisite number of hours to be so. He was young, keen, extremely good company and above all a very good airman and operator.
Training and culture also have their part to play and I think I may be happier with very young crew in some countries than in others.
Doc C