I do run the A/C in our camper, but we are in humid FL. Greatly increases the life of the interior if kept dry and around 80 degrees.
It's also healthier for the A/C to run a few times during the day, rather than sit dormant for many months. Keeps the seals lubricated. Our camper is almost 9 years old, and the A/C still works like new. The A/C on a previous popup camper died after 5 years, and was only run when actually camping.
The cost to run ours isn't much. Only runs briefly during the peak hours of the day. Camper is well insulated, and doors/windows kept shut.
Wax? Definitely!