Besides the cost of electricity, is it detrimental if a computer never goes into sleep mode? Obviously, servers are running 24/7, but is it different for a personal computer?
closed as not constructive by Diogo, Tom Wijsman, slhck♦, Andrew Lambert, studiohack♦ Mar 23 '12 at 18:44
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The only kind of damage to a computer from leaving it on continuously is that fans on desktop computers tend to stop after X hours of continuous operation (due to dust contamination).
If your computer doesn't need to be on all the time, you will save money on your electrical bill, and if you think about your 'carbon footprint' you should be aware of what is being used to make the electricity that you're using; Are you causing more coal to be burned, or are you running on hydro-electric power, or nuclear?
Powering down your computer completely, and sleeping your hard drive will actually be harder on it, most sources I've read say that hard drive spin up is its most important wear and tear for rotating hard disks. A solid state drive machine of course will not be similarly affected.