You probably will not use more than about 10 gallons per week. Usually you can refill a propane tank in most cities. Unless you will be parked in the center of a dry campground, such as being at the Circus or fairgrounds and can not move the RV for 2 weeks, you will find that you can refill both the diesel and propane tanks in most every town that you visit.
I would keep the water heater hot if the temps drop below 32F out. Just my thing, I don't want the water heater to freeze and crack. If the RV is totally winterized, and you do not run any water through the lines, then you can leave the water heater off. If not full of water, you can not run the water heater or it can melt. But I have used my RV, water and all for a 2 week time at 19F overnight temps in the desert, and everything worked normally. I did not use the 18 gallon propane tank up.
In the summer, I normally use 14- 16 gallons and refill every 6 weeks while full timing. I never went to a town and was un-able to refill the propane tank.
Fred.
