Mine is always on. Other than a bit of electricity use, I don't really see a reason to turn it off.

Things like updates and spyware or virus scans or defragging can be scheduled and done in the middle of the night also, so I don't have to bother when I'm on the computer.

I used to leave mine on but mow that there are 3 of them in the same room, it sure heats the place up and the electricity use would be higher.  So now we usually turm them off, at least 2 of the 3.  

a matter of personal preference, mines always on saves me having to find the on button without enough caffiene to activate my braincell in the morning   

I'm on all the time!

Yep, same here, heard it was bad to shut the darn thing off and on, but you know what, it does collect alot of dust in the fans when it's on all the time. You will and should change your fans every year, I do. I buy them on sale and hubby or son put them in. If your computer doesn't sound quiet while on it is on, most likely the fan is dirty. Take care to check it out...mschleisner

Ahhh & I hibernate, darn cold here in Canada

It's My Secret

I turn mine off when not in use
for say 3 hours or more   
old school computers were better
to leave on , but newer ones can
be shut down without worry ...

Mine only gets shut down on a software install restart or a SystemMechanic restart...or when the little one finds the button that Dell so conveniently placed.

Computer on.. Monitor off

I use sleep mode to save power yet wake up faster than turn off. Best of both worlds IMHO.

Off.

Spend money on electricity if you like, but that is eating up the world's resources.

One problem with leaving them on....case fans, etc have a finite running life after which they'll be rather noisy, if nothing else.  tens of thousands of hours sounds a long time...but I for one have replaced all the fans in my case since new....

About 10 years ago, someone brought their PC in to my shop for repair/diagnosis.
His PCI Video card had literally burst into flame and melted. Had he not been present I am sure a fire would have started.
Use your own judgement but turning them off does not hurt them.

We have thunderstorms so often I sometimes have to turn all the office computers off while they pass.



Same with TVs, Sound systems and anything with a little red light glowing after you turn it off. I've read where the "stand by" drain on electricity is pretty overwhelming when applied globally. That's another reason I keep most everything on a power strip/switch that I turn off when not in use.

on all day...sleep at night, reboot once a week to clear the ram.