I would wait until early January to order them. You will need the voucher as they ask for the numbers on the back. They will actually tell you which month they expire so when you call, make sure and ask. They are activated upon ordering. Right now it takes approximately 3 weeks to get the card.
I'll tell you my story and that should help you.
I called last Friday on November 4th to order my card for December 9. When I called the person asked when I was going. She then told me if I waited and called back on Monday, November 7, the card would expire in December 2006 not November 2006. I really appreciated her telling me this. I then called on Monday and they took my order and told me if the card did not reach my home by December 6 to call back and they would have a temporary card for me at Epcot. They required the numbers on the back of my AP voucher since I do not have the actual AP yet.
Good luck.