macOS High Sierra drops printer connection
I am having the same problem with my Canon MF733C using Bonjour. Both the printer and the scanner will go offline after some time. Power cycling the printer or removing and reading the device "fixes" the problem until the next time. I am running 10.13.3 with the latest printer and scanner drivers from Canon.
I have tried the Canon drivers using Bonjour / AirPrint and now have the scanner configured using the IP address of the device to see if that helps.