So I turned down the difficulty still goes dead after a couple hours, Does anyone have any ideas about the script though, I just need the card to last another month or so till BFL comes out
Try blowing the dust out of the heatsink with a can of compressed air, but anyway, to answer your question...
If you're running on windows just click... Control Panel > Administrative Tools > Task Scheduler > Create Task
on Gnome GUI Linux its..
sudo apt-get install gnome-schedule
Applications > System Tools > Schedule Tasks.
or from linux command line search google for info on "crontab"