I have a PC in a spot of my house I can't get a cable to. But that's the PC I do my Blu Ray ripping and encoding on, so I keep a 5tb external drive for moving the files to my NAS afterwards. Sometimes it would take days over WiFi instead of minutes to hours over USB 3 twice. (and piss off my wife for saturating the wifi, heh)
Hard drives are fine. But replacing them every few years for fear of failure is a waste of money. Drives can last over 10 years, or 1 day. Just have more than one copy and you'll be fine when one does fail.
My experience with powerline is pretty terrible. And there is no better place for it sadly.