We recommend leaving your computer turned on when not using. If you are going to be away on vacation or something for a week or more, then turn it off while you are gone. Otherwise it’s better to leave it on for several reasons. The only drawback to leaving it on is that it will use a little more electricity. Desktop computers don’t really use that much electricity and laptops use even less. You can set your computer up so it turns the screen off to save some electricity.
Here are the reasons why you should leave it on. The main reason is that if you leave your computer on, it can do updates and maintenance while you aren’t using it. If you only turn it on when you are using it, it’s going to do all of that stuff while you are using it, slowing you down and interrupting what you are trying to do.
Hard drives (not SSDs) are happier when they are at a consent temperature. When you turn your computer off, it gets cold. When you turn it on, it gets hot. All of that hot and cold shortens the life of a hard drive.
If you leave your computer on, then when you come back to it, you can get right to doing what you want to do. If it had been off, you would have to wait for it to boot. Computers are usually very slow the first 5-15 minutes after they boot up.
You may be wondering if putting your computer to sleep would be a good compromise. Nope. Putting it to sleep instead of powering off only gives you the advantage of faster startup. It does not allow the computer to update/maintain itself and the hard drive will still go cold.