At least have a line verification after each G-Code line is done. Save it to the SD-Card. And when power comes back on, have the printer resume from that point.
Unless it disappeared in a firmware update, the X1 has always had power fail recovery. I’ve only tested it once by fumble fingering the power strip it’s plugged into. After it booted, it said it had detected a power loss and did I want to continue? I tapped yes and it completed the print. If it’s been off too long, you may not want to continue as the print may come off the build plate. Depends on filament material and build plate.
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I’ve managed to successfully restart a very long print after a planned power down a couple of times.
Both times I used the cool plate, plus also didn’t power down until I had paused the print and allowed the extruder to cool down to below 50 degrees C.
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Thank you for that information. Happy Printing ! 
Thank you for your reply.
Just get a really huge UPS!
Boom! Problem solved!