I've said this in many other threads, but my personal preference for backing up my photos goes like this...
I have Google Photos (formerly part of Google+) and Microsoft One Drive both set to upload my photos while charging and connected to wifi. I'm constantly on wifi at home and charge my phone every night, so my pics upload to 2 different cloud services while I sleep.
I also upload the ones that I REALLY want to keep to Facebook, so the best pics are backed up to 3 different places.
Again, just my personal setup, but I don't have to worry about problems like this. If my pics disappeared from my phone for some reason, they should be in at least one of those locations. I like Google's better, because I'm able to select which folders on my phone I want to upload from. That way, I don't get pics I downloaded and screenshots that I don't really need backed up.
I think Dropbox might offer the same ability, but I can't recall.
Either way, with all of the free storage and automatic backup options available, I just keep spreading the advice here, hoping more people will catch on to the benefits.