Walking at 7 months is pretty pointless. Use the Resort Availability Tool to make sure 14 nights are available to being with. Book the first 7 nights as soon as you can and call each day to add one more night.
The idea of walking is that you book dates earlier than you need, adding and dropping one day each day until you eventually end up with what you want. Since you can book 7 days ahead at the booking window, by booking the days in advance of your reservation, you can lock up the room so nobody else can book it. But, since owners can always book ahead of you, you could always lose a day while walking your reservation.