I don't turn off my PC. I prefer to leave the machine running all the time so that I can just sit down at my desk and get started immediately. I hate the waiting game. I pretty much can't wait for anything—boot time being one of those things.
To me, having access and data on a moment's notice is important, so I do everything I can to make sure that my PC is ultra stable. This means no overclocking (seriously), excellent cooling, and uninterruptible power. Everything is connected to uninterruptible power supplies (UPS), and I use more than one. Being able to not lose power during a black-out is extremely helpful, especially when you're in the middle of a boss fight or writing that all important hardware review.
The longest I've had my PC running without shutting down is 416 days or so. I only shut down after that because of a massive hardware upgrade, but otherwise, it stays completely on. I also use several UPS units for my NAS units, which definitely need to stay alive.
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