I have two computers:
one will turn off the screen in 1 minute
the other will display the screensaver in about 6 mins and screen off in 20mins. In power saving mode it will go into sleep in 40 mins and hibernate in 6 hrs.
I have the first computer on up to 2 weeks in a row, to download extremely large files. all I got was a $50 increase in my electric bill.
I have left the second computer on up to 2 days or 3 in sleep mode. I'm sure nothing will happen if I left it on24/7/365, but I'll owe the electric company about $12,000 by year's end and about 200 tree huggers/hippies will be picketing my house because I use too much electricity.
the first computer has a 250 watt power supply,generally it consumes about 115 watts.
the second computer has a 950 watt supply and consumes around 500 watts. because California is full of hippies and tree huggers, I will get fined or probably arrested if I use too much electricity, easily done if I leave #2 computer on 24/7/365.