I think there is another informative thread on this...Surprisingly, many do the same as us.
We just went full time this week and plan to move around a lot - but will take advantage of off season rates and for month long stays, you get a discount.
We were extended stay from last Sept until FT. We bought a new RV in Sept and were given an Elite Good Sam membership (basically, we get 10% off on GS campgrounds and Camping World Stores), we bought a 15 month Passport America for $39.95 that gives 50% discount in their selected campgrounds (always read rvparkreviews.com - we've discovered you get what you pay for! But for an overnight stay, we can tolerate about anything-except staying in a Walmart Parking lot - we're addicted to full hook ups!
The main place we began to stay in for extended periods was a KOA campground - near our daughter and reason now why we're in this RV finally (DH dreamed about it for years). We joined - I don't think we paid a fee - I don't recall! They are a bit expensive, but you get what you pay for! They are consistently clean and well-run. Once when making a reservation, they asked if I wanted to use any of my 45,000 points? I had no idea we also earned points in addition to the standard 10% discount! So we get a free night every once in a while!
My step dad and another long term traveler believed in RCI and 1.000 Trails and Coast to Coast. But they paid very high fees and in the end gave their memberships away to get out from under their maintenance fees.
Hope this helps and happy trails!