Last night. I shut down my computer every night. Have for any computer I have owned. No reason to keep them running when you are not going to be using them for a while. I even put mine in sleep mode when I think I will not use it for a while during the day.
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I think it is best to shut it off. Some issues with a computer, need what they call a cold start. In other words, a complete shutdown and restart. While that may not be as much of a issue as it use to be, I still want to shut it completely off before I go to bed. Sleep mode helps some, by not having your fans running more than they need to be and thus reducing the amount of wear and the dust collection inside your case and on the fan blades.