RV Parks/Resorts that are frequently used by "Snow Birders" every winter require reservations 8 to 12 months in advance. Areas like Arizona, Indio, Ca., or Southern Calif. need reservations well in advance. Winter season generally means Dec. through March. The longer your reservations the lower the cost. i.e. 3 to 4 month reservations are much lower than I month. Flying by the seat of your pants and trying to make reservations as you go in popular RV areas is not a good idea. " you have everything to lose and nothing to gain" by not making reservations well in advance. Reservations do not lock you in to a rigid route trip, you can always call and cancel. Just make sure you ask what the cancellation policy is for each reservation you make.