There seems to be all kinds of rates and renewal rates out there.
I got a Thousand Trail Zone Pass when I bought a MH last year. I never used it until last month when we stayed four nights at a campground in Clermont, Fl. I had an option to renew for a year at $525, which really wasn't going to be worth it for me. A few weeks back I received a letter from TT offering another year for $199 or 2 years for $399. I renewed for 1 year since even if I only use it 3 or 4 nights during the year, it will have paid for itself.
I also wanted to keep myself eligible for what I assume will be relatively low renewal rates in a year and a half or so, when my wife retires, and the two of us will spend more time traveling.