With my truck camper I did the wire to the running lights so when I turned them on the camera was on. Worked great!
On my Class C they have set up the running lights to be on as soon as the key is turned on (not the head lights just the running lights). Good idea except the lights on alarm goes off when you stop and open the door until 3 minutes later the running lights shut off. This would work for a camera as well but it always has power.
I contacted the manufacturer of my back-up camera for the truck and was told that they do not recommend the camera always being on as it was not designed for that.
