Also consider the possibility of using one airline down and another back. We live near BWI and have used SW one way and Airtran the other. We like nonstops, and between the two we can usually get a good flight at a good time. Also check different days, as Sunday is usually less expensive down (although not always), and Saturday less expensive back. We booked a trip starting Sunday Dec 2 through Friday night Dec 7. When air fares became available we added a night on the 1st at AKV and and are flying down this Saturday morning. We'll be jammed into a studio with ourselves and my DD, her husband and our 9 mo old grandson (be glad to move into our 2BR BCV villa per our original ressie).
So if you book the minimum trip at 11 months, you can add on later or stay in a value for a night or two (I know moving is a hassle but can be done if needed). Another good thing is that in a pinch you (and us) could drive to WDW with about 15-16 hours of driving. I'm not saying I would want to, but it can be done, and a few years down the road when I'm retired I can see doing this. We have friends with time shares in Aruba, and airfare there is a crap game with no other way to get there.
So as others have said book the room first, at least the most important part of your trip, and then watch for airfares as they are released.
Jean and Bob