I also did something similar, plus all my home automation which is 98% local-first|only. My trip was just 3 weeks but on the first day leaving, between one plane and another, my power company had a 4hours extraordinary maintenance cut, my UPS didn't last enough and with that blackout the RPi SD card died, and I was locked out my LAN for all the trip.

Lesson learned: configure the UPS to communicate with the servers and shut them down in a controlled manner when batteries are dying.