We have been full-timing for 5 years and use Good Sam, Passport America, KOA, and Escapees. We have investigated the time share type places, but they seem regionally spotty and to make them pay you have to use them.
It really all depends on what your travel goals are and where you like to camp. We are not boon dockers and with a 43' 5ver don't stay in many state parks. We like travelling and spending time exploring history and the sights in areas we visit, so rarely travel m,ore than 200 miles in a day, not do we make lengthy itinerary plans that tie us down. We have often planned to stay one or two days in a location, then changed based on what's in the area and stayed a couple of weeks. Other than our 3-4 month winter stops in FL or AZ, we rarely stay in one place more than 2 weeks - though we have stayed in "target rich environments" for a month where there was lots to do within 100 miles or so.
I'd recommend NOT buying into a Coast to Coast, etc type plan until you've been on the road a little and see what you like. Had we done so, we would not have gotten our money out of it, but YMMV. Most have "look see" type arrangements so you can check them out.
Keep researching and have fun!
