This thread is 4 years old, and no one will read this message, but..
My AiO is still going strong in our kitchen. Between email, shopping, finance, kids homework, and the TV card (Win Media Center software and remote control), it has probably been used on average 6 hours a day, approaching 10,000 hours. The cost per hour for this computer (not including electricity): about 6 cents. Not a bad woot.
BTW, part of this computers longevity is due to my constant OS refreshes. I intentionally kept mine at Windows 7. I restore a drive image every year, and let it install updates (OS, Java, Adobe, MS Office, etc.) and then I create a new image to be restored the following year. All of our docs are stored on a user partition that is backed up over the network, though in the past few years, cloud storage has really gained momentum (drive, photos).