@roxx - You can always create an ISO file of your SD card. You can restore from that if your SD card becomes corrupted.
I find that copying the config.js file is 90% of the way there. It will list the modules that you have installed, which you can download fresh from GitHub with little problem. The config file will contain the API keys, so that’s the part that individual to your mirror in most cases.
Having a copy of the Raspbian image on hand is probably another 5%.
Spinning up a new Pi with a given config.js isn’t that hard.Flash the Raspian image to SD card and boot to it. Remove unwanted features (Wolfram Alpha, Minecraft, LibreOffice, etc.) Update, upgrade, distro upgrade. Install Node, Electron & XScreenSaver. Configure screensaver to never save the screen. Clone Magic Mirror & npm install Restoreconfig.js from backup. Clone & npm install the modules listed in the config.js file. enjoy!