I kind of agree with your belief there. Anytime you keep anything at a moderate temperature, rather than extreme hot or cold, it's gotta be better for it. The question is - when is it cost effective to do so?
Being in Idaho, I'm going to assume that you probably have a fairly long and cold winter, similar to Wisconsin. Then again, Idaho is a big state so you may have it a bit better than we do.
If you want to heat it, it will cost you in energy, regardless of which method of heat you want to use.
If you want to use the heat pumps, you are probably not going to be able to run them on a 20 amp circuit. The other caveat is that heat pumps don't work well below 40 degrees and they ice up once you hit 32. It's a very inefficient way to use electricity. The advantage is that there is no "tank" to run empty because you are plugged into shore power. It sure does make the light meter spin though.
Ceramic heaters are nice as auxiliary heaters for when the coach is occupied but I wouldn't care to leave it on while unoccupied because of concerns of fire. It also doesn't circulate the heat around the whole coach.
The propane furnace is the best method to heat the coach. It is easily controlled by the thermostat and the blower fans will circulate the heat all around the coach. The drawback is that sooner or later (probably sooner) you are going to run out of propane and you'll have to refuel. You can add an ExtendaStay tee to your coach to allow feeding it by an external 100 lb tank. At least that way you don't have to move the coach to refill the tank. You just have to swap tanks every now and then.
The biggest decision you will have to make is - Is it worth it? I don't bother because it would get pretty expensive and I haven't seen any damage from sitting in the cold and, for the short times I do heat it, the propane gauge does drop a fair amount.