I don't have anything to keep me awake.

I figure if my body's telling me it's tired I'm better off listening to it. Even if it is short naps. In a crisis I need all 4 cylinders (i.e brain cells) running as well as possible.

Sleep deprivation has it's costs that could affect someone's survival in decreased reaction time/judgment/ etc.

I remember vaguely some studies out regarding residents and the number of medical errors that are made when they pull very long shifts without sufficient rest.