My experience as a professional musician got me into the bad habit of leaving everything powered up 24/7, as there is nothing worse than having the inspiration disappear after you've powered up 8 or 10 devices. Now I leave all but the power amp on, all 16 PCs in my home and office on 24/7, the only device I turn off between uses is my home backup drive, since it only gets used for about 20 minutes a week, to save the drive and also avoid those blasted "accidents" that seem to befall backup drives...
Someone posed the exact same question here a while ago, the consensus was powering down saves money, but not necessarily gear. I also have processes that only run when the PC is idle, plus in my hectic life I don't like to wait for my home machine to boot before I can use it.
On my work machines, I demand everyone to log off (not shut down) at day's end, including myself. This ensures no open files during the nightly backups, the latest synchronization, and saves energy as there is no possibility of the machines being needed overnight.
I think common sense comes into play also, of course CRTs should be power-schemed to shut down on their own after 20 minutes or so of inactivity, but they wake right up. It's a battle between frugality and efficiency.
It also seems many PC problems occur at startup, so leaving them running prevents the power surge acewarlock describes. Not sure if there's science to back it up, but it makes sense that a moving part, like a hard drive, will endure greater stress from a cold start than if it were left warm & running between uses.
Be aware, though, that a surge suppressor "wears out"
This is something people just don't "get", but it is true. I'm not sure if there's a test to make sure it is good but 5 years is my rule of thumb. Great advice RICHINMINN.
Tony
"Buy what you like, or you'll be forced to like what you buy"...me