I don't currently have a backup setup, no.
Since the drives themselves are decently fast and my 970 handles most of the grunt work, I'm mostly looking to consolidate for ease of use. I'd be fine sacrificing some storage space to cut down on the number of locations I can save things because it got a little out of hand before.
If I were to throw the two M500s in Raid 0 how concerned should I be with having one die? Would it be fine to disconnect one to do PC work and reconnect it after so long as the system never received power?