The oldest part of our setup are the Denon stereo receiver and the Infinity speakers. I bought them in 2000 and they have been playing at least 5 hours per day on average. That would be over 23000 hours.
My Macbook is over 5 years old. It's had a hard drive failure but other than that it still works as good as the day I bought it. In fact, it works better than when I bought it. It came with Leopard (10.5), it has run Snow Leopard (10.6) and now runs Lion (10.7). The extra 1GB of RAM I had installed when I bought it make all the difference though. It's even a decent PC (Windows 7) when rebooting through Bootcamp.