[Null]

it can over heat. which just means it'll fry itself... unlikely to start any fires.

but from what I've read, you do NOT want one of those cooling unit things for it.. they make matters worse. something about a fan being on top of a fan, doesn't circulate air very well. it should be fine if you use it like normal.

I've left the thing on for 5 or 6 hours while I've been out. or i set it to download a few things and leave it on during the night while i slept (because their servers were downloading really slow at the time)

its actually more likely to over heat while its doing a lot like playing a game rather then overheating while just idling there. but honestly if its doing NOTHING there really isnt any reason to leave it on.