I spend the whole summer parked in Yellowstone which averages really low humidity. Usually get away with defrosting once. In the winter, we are in Florida where the humidity is, oh, 250% most days. We defrost every two to three weeks.
I know it is contra intuitive but if you fill your freezer as much as possible, you will reduce the amount of moisture laden air, reducing the rate that frost accumulates.
If you are getting ice on the fins in the refrigerator, a little spray bottle full of alcohol is handy to spray the ice off with.
new (usually dirty) Nissan Titan XD (hardly paid for)
Middle-aged Safari SE
Young, lovely bride