When I was a kid, my parents were always adamant that the computer remain on at all times—rebooting only when absolutely necessary.
The logic was that the surge of power when turning the computer on would shorten its lifespan. While this is true, leaving your computer on 24/7 also adds wear and tear to your components and the wear caused in either case will never impact you unless your upgrade cycle is measured in decades. If your only concern is to maximize the lifespan of your components, neither option put you ahead. So why should you leave it running?
Leaving your computer on is convenient. Instead of waiting for it to boot you can hop right in and get to work or play. With SSDs, boot times are significantly reduced, but if you have lots of programs set to start with Windows, it can still take a minute or two to get started. On the other hand, while the “sleep” function in Windows typically works as it should, sometimes your machine will flat out refuse to wake up and you will have to restart anyway. For some people, they have lots of productivity programs running all the time, so rebooting can be a hassle.
If you’ve made your computer accessible over the internet it will do you no good if it’s not running. Having the ability to remote into your machine from anywhere can be a lifesaver. More times than I can count I’ve rushed out the door only to realize I’ve forgotten to send an important email, or to send myself some file I needed access to throughout the day. And, if you’re running something like Plex, you can access your media library from anywhere if you get out of the habit of always turning off your computer.
Turning your computer off when you’re not completing tasks also means that your computer can’t complete its own important tasks. Processes like virus scans and system updates will have to run when you’re trying to get things done. These tasks can be resource heavy and inconvenient. If you leave your computer running you can schedule these to run overnight or anytime that’s convenient for you.
While there are lots of compelling reasons to keep your computer running, there are some scenarios where it’s definitely best to shut it down. Electricity can be expensive and sometimes every cent counts. If you are concerned about energy costs, leaving your computer on all the time will reflect on the utility bill.
If you are running custom water cooling I would also recommend not leaving your machine running. Should the pump die when you aren’t around, the results could be catastrophic. Whether or not you leave your computer running will largely depend on what matters most to you. Luckily for us, there is no wrong answer.
I still prefer leaving my system on all the time, but once in a while I'll check the health of the fans and pumps. Thank goodness for side windows.