And, of course, there's always putting it to sleep. You sleep, why shouldn't the mini? It wakes up a lot faster than people do!
Leaving notebook HDs on 24/7 is not considered a good idea, leading to higher failure rates. Since the HD in the mini has easier access for replacements, that's perhaps not as big a factor as it is in expensive repairs of notebooks, but there's always the hours and $ spent in putting in a new one.