For the truly paranoid you can set up a RAID array. Certain configurations allow the loss of 1 drive but still have recoverable data. Also all drives are not equal. There are consumer grade and enterprise grade drives.
And what if you catch a virus? Will it be on your two drives too? At least you will be sure to keep the virus if one drive crashes...
Ah, you must be a porn-surfin Windows man. Use Linux, don't catch viruses. Hey Scataphagos have you measured the wear on your SSD? There are various tools out there to give you some idea of how "used up" the Flash chips are.
Linux, no viruses???? https://en.wikipedia.org/wiki/Linux_malware http://www.tecmint.com/linux-operating-system-is-virus-free/ Porn surfers use a Mac. I use Windows for decades. Never had a virus. Never had a SOA too.
The only measure I've used is Intel's "SSD Toolbox". All of mine are still reading "100% of life left"... some of the drives are 6+ years in service. In all but extreme "write intensive" applications, it seems "SSD wear-out" should be a most minimal concern.
Leave my PC all the time, switch off the screens, yes it costs but it's torrenting and available if I need to remote access into it, like first thing in the morning. Light bulb wise, long tube flouresent jobs that approx 20seconds of run time to start up, so basically if it's off for longer, there better of, off, power savers the same, normal old fashioned lights zero time really so on/off as much as you like. 18months on my SSD not worried about it at all, the fact it's literally dangling out of the side and has been for 6months+ is another issue, but be fine, wouldn't get away with that kinda abuse on a old spinner.
If you have no need to leave your system online then just suspend/hibernate/sleep it. It'll restart prior state much quicker and not burn energy spinning fans and keeping memory/cpu powered up.
There is also the logic of heating up the components then cooling by switching off causing damage aa this makes them expand and contract. PCs are cheap, so not a huge issue these days, although 5 year replacement cycle these days compared to 2 years ages ago.
Perhaps not even that often. I've run Dell Precision workstations until nearly 10-years old for trading. Current crop was bought off lease from DFS when they were 3-years old and are now 6-years old (still plenty fast enough for my use)... hoping to keep them running until W7's end of life. In case they don't, Dell's Precision T5810 will run W7, W8, or W10.
Trying to remember my PC's spec 10 years ago, think I've only done 1 upgrade in 10years maybe 2, I do bottom of the spec aswell so 1 - 2 year old processor. Unless your playing games, then it doesn't really matter really.