I want to run my Radeon 6850 on Furmark at night so I do not need to run it 6 hours when I would like to use it. I do not want the card to get too hot at night and break when I am not there to over see it. Is it safe to run Furmark at night for 6 hours, or will it get too hot and do damage maybe?
Run it for about 30 minutes on the day and keep an eye on your temps, it'll reach a point that it just won't go up anymore, that's usually within the first 15 minutes. That should be enough for proving card stability and if wether it'd be safe to leave it overnight.
Unless you're doing lots of overclocking and tweaking voltages, and if your games and apps don't have any problems, then you don't need to run furmark for anything over an hour or so if you just want to prove stability, it just shortens the lifespan of the card, GPUs aren't meant to be tortured in such a mean way you know.