To be honest, it depends on the card you have. I know folders that have run some cards for ages and ages and had no issues. Others have problems after only a month. But like I said, if it fails within waranty your covered. And warrantys normally last a year. If things go well and bitcoins DON'T just die out ( only requires more people signing up and using them to not) you could make 2600 a year. - your electrical costs. So if you card fails after warranty you can buy a new one with your profit anyway.