Agree with "brirene" we also live in AZ why would you ever have to "winterize", not required.
We boon-dock on the Rim, Morman lake area, we travel to Denver, Seattle for short 2 week trips in the winter (xmas). We NEVER winterized. I make sure the fresh tanks are full (yes we travel loaded) and make sure I run the OEM heater. We set it at 74F Northwood is designed for this type of use.
Make sure your heater system vents to the galley, if it does do not worry about it.
In AZ I do not see a reason to winterize, but I have not used other brands other than Northwood.