Your idea on changing the sleep thing is good, BUT it's often postulated that people in space would likely go to the Awake 2 or 4 hour model with a 30-minute or 1 hour sleep in-between (like people on submarines sometimes do). I've personally done the 2-Hr. version for weeks at a time when working on coding projects and there is a curious catch to the idea of only needing 5 hours of sleep a day -> IF YOU DON'T TAKE THAT NAP WHEN YOU SHOULD, you get so tired you can't keep going. You start making dumb mistakes, dozing off and the like. Having a sleep-power reserve like some watches do might be another good resource to manage. As you get too tired, you might mis-read what resources are on a world and waste a bunch of time when you realize it wasn't real (like a mirage). OR maybe your character just dozes off uncontrollable. This could be a fun, real-world management issue.