Call me a tree-hugger if you must, but I see no reason to keep a computer on when it's not in use. That wastes electricity, which is bad for your pocketbook and bad for the planet. And it's probably bad for the computer.
Yes, I have seen occasional arguments that shutting down a computer, then starting it up cold, cause more wear and tear than leaving it on for 12 hours. I just don't buy them. All computers potentially suffer from heat problems, and one that never gets a chance to cool down will suffer from more of them.
Besides, a computer that's off is a computer that can't be infected with malware or behave under orders from afar if it's already infected.
If you don't like starting your computer fresh every morning, you can hibernate it rather than shutting it down. From the hardware and power-consumption points of view, there's no difference between shutting down a PC and hibernating it. But there is a difference in what happens when you boot it again in the morning. A shutdown PC will give Windows a fresh start, clear of any digital cobwebs it acquired since its last boot. A hibernated PC will wake up where you left it, with the same programs, files, and windows open.
Which you prefer is a matter of personal choice, although you should probably shut it down at least once a week to clear those cobwebs.
