It sounds similar to aviation. I considered diving into a career track as a pilot once, but you've got to start young or there's no point. Mandatory retirement is at 60 (if I remember correctly) and its all based on seniority. Since the best earning years are at the end, there's little chance you'll ever get to touch a commercial airliner if you don't start working in your teens. Since I didn't have the resources to take flying lessons until my mid 20s, it was a hobby only. (Plus I've got this irritating habit of falling asleep in the middle of the afternoon.)

Actually that makes me curious. Have you written anything about handling fatigue on those long hauls?