Brain Fertilizer

One interesting thing in Jagged Alliance 2:
Your characters tire the longer they are awake. But rest helps them recover. Sleep helps them recover faster.

...but they don't ever actually have to sleep. Continuing to rest for long enough time (during which they can be studying/practicing to improve an attribute) will fully replenish all energy points.

If they do happen to fall asleep because you worked them too long, you can go to the screen and click on their comatose body. They will rise wearily to their feet and sway with exhaustion...but you can then give them a study assignment which will make the most efficient use of their time.

But when traveling, you can't study anything, so you might as well let 'em sleep to get their energy up as rapidly as possible.