I also received a zone pass in Mar. 2013, when I bought a new RV. The first time I used it was about a month or so before it was to expire. We went to Clermont Fl. and stayed for 4 nights. The place is huge with over 800 sites and not bad, considering it was free. :B
They sent me info on renewing which I didn't intend to do, at was going to be around $500. They eventually offered a one year, one zone renewal for $199, which I ended up doing. Since then, I've been back to Clermont twice for a total of seven nights, and spent four nights at the Wauchula TT, because we couldn't get the 4 nights we wanted at Clermont, between Christmas and New Years. Wauchula is considerably smaller and not as nice, in my opinion, as Clermont. They also had electrical issues in one section, which appear to have been going on for years. We are going to Clermont later this month for four nights. The only other Fl. TT park that I can go to is in Wildwood, where I have not stayed yet. I believe you can also use your TT zone pass at Encore parks and receive discounts under certain conditions.
Another consideration is that each zone pass covers a fairly large part of the country. Some states have more TT parks than others. I believe the southeast zone pass stretches from N.C., down through Fl. and as far west as Texas or something like that (I don't have their brochure in front of me).
From what I"ve seen from talking to others at Clermont there are a bunch of different rates, programs, what not depending on when and how you got your TT membership. I believe as others have said the zone pass is a year to year deal and no big bucks are involved getting in or out. Then again I haven't opted out yet (renewal at whatever rate will be coming up soon) so don't know if they will hound me if I choose not to renew. :B
2014 Itasca Spirit 31K Class C
2016 Mazda CX5 on Acme tow dolly- 4 trips ~ 5,800 mi
Now 2017 RWD F150 with a drive shaft disconnect