No you can modify your 11 month reservation using the modify tool online. To do this go to you 11 month reservation and choose modify then use the booking search tool that comes up to search the dates you want at whatever resorts your interested in. If you find availability and want to switch continue with the new reservation and it will let you know that your original reservation will be switched out to the new one. The modification tool holds your original reservation until your new one is booked so you don't have to worry about ending up with no reservation.
Good luck!