I believe TT only lets you reserve 3 months ahead.. And in Flordia, In the winter, You that means you make your reservation 90 days in advance, 88 days and they are likely sold out.. Thankfully you can do it on the web. USE MSIE though, not Firefox.
OH, The park in Fair Play SC (Carolina Landing) IS open in the winter and though there is on other membership park I can visit for my week out there are some government parks I can park in for 10-12 dollars a night in the area.. And if you are Catholic,,, You get to hear me sing in the choir

(If not then I can help you find the church of your choice, No problem)