Keeping duty times is a serious thing. I remember when I was a truck driver in the army, I was out driving the whole day during a maneuver in winter, and some sergeant wanted me to take a guard duty shift, essentially cutting my sleep down to three hours for that night. I flat out refused. I wasn’t going to drive a seven ton truck with a dozen men in the back around on icy roads after hardly getting any sleep. Of course, it’s easier to refuse when you’re drafted and don’t care too much, than when it’s your career and you don’t want to disgruntle your employer.