Last question for today, honest! (maybe)...
I know you sweep gems from skills to the fatigue box at the end of the hero's turn. What about gems spent by heroes during the overlord's turn? Do they sweep at the end of the OL turn or do they hang out on the skills until the end of the next hero's turn? This would occasionally matter due to exhaustion limits on "anytime" spells or other special skills.
This "sweeping" is also the first thing done in the heroes' turn (as well as the last). See page 19 of the Heroes' Book.
Edit: Jim ninja'd me, but i provided a page number .