You need three copies of your data: the working copy, the nightly backup, and the offsite backup in case of natural disaster. I physically mailed a drive to my father in another state in case my building catches fire. You can also use a safe deposit box or give a drive to a friend who is geologically separated from your location.

Notice: recent info suggests that SSDs suffer bit-rot when not powered. Not enough confirmed info at this time for me to go into it further, but please rewrite important data from time to time.