I know we got a 1 day ticket that was required for free dining (this was in 2008 or 2009 and we already had an AP). I saved it planning to use when our APs ended....but of course put it in that "safe" place and it was years before I found it and used it in 2013.
I don't think unused tickets have any expiration do they? I know if once you use a ticket it expires in 14 days, but I think you could buy it now and use it years from now. Not sure that's the wisest choice financially....and be sure to put it somewhere you won't forget, lol....but I think you could buy them now and if something happened and you didn't go in Dec/Jan that you could hold them for years. Disney would probably be thrilled to have your money and not have you use your ticket, lol.
Reminds me of the news article I read every Christmas about people giving gift cards and how it's some million/billion dollars of gift cards that are never used. That's some profit!
You're going at a very busy time, but the parks will be beautiful and the weather will be awesome. Enjoy!