My computer has been on non-stop for four months now. I turned it off once about a month ago to install a new video card. My record is probably 6 months, I'd reach higher milstones, but I move back home at the end of each semester.
I figured it out, and it only costs me 7 extra cents a month to have my computer on 24/7, barring of course I keep the monitor off when I'm not using it.
