Been camping most of my life, and RV'ing for more than ten years - we use a combination of military, state parks, and national parks. I can't remember the last time we stayed in a private campground.
We have it on a 4x4, and can get in anywhere with no length problems - so that makes a difference in how we camp too. We usually stay less than two weeks on any place, and often only a week.
I full-timed for over three years in a truck camper, and we now use it about seven to nine months of the year, with a condo for some off the road time - repairs, etc.