I shut down my PC at night, it's only on when i'm present in the house or if i'm buying groceries which takes 10-15 minutes.
all that carbon dioxide...I think I'll buy a plant and post it in the room. the bioelectronic circle of life.
Trivia : One puny plant can hardly suck up 10% of the CO2 emitted by computers, you need a dozen potted plants.
I sometimes left it on for an extra three hours or so to advance some downloads, because I used to have a monthly download limit and traffic from 1 to 9AM didn't add up to that limit. That was rare though, and ended now that the limit's gone.
My main reason why I do it BTW is because of the DLs, and Torrents. I wake up using my computer's alarm clock. If I didn't I could wake up in 12 noon
I always leave my home computer on during nights as well as the whole weekend, turning off the monitor if I am not in front of it. On the other hand I alwasy turn it off at the office if I am not using it, we satrted turning off the server as well.
Done it couple of times. Just to seed and leech torrents. Turn off LCD screen though because you dont want to burn screen.
I've only ever done it once, whilst downloading Garry's Mod. Looking back on it, there kinda wasn't any need, since I could've paused the download... Meh.