First off I would suggest that you have a usb stick with a backup of your kemper near - I always keep one in the rack of mine.
I never had the case that my unit "quitted" and I wasn't able to use it anymore for the gig. Maybe 2 or 3 times (in 3 years extensive use) I had the unit become unresponsive to control inputs from the remote, but that was quickly resolved by rebooting.
However, If you want to be on the safest side, look for a small footprint backup rig like a helix stomp or even a strymon iridium.
Hope that helps