I don't have my DDE card on me, but I think it's actually 13 months. I will try to post later with the date son mine.
Oddly enough, I have done three trips since I got mine, and I've hardly used it at all! The problem is, two were solo trips, and I feel weird eating at a table service restaurant by myself. I'm hoping to plan a trip for me, DH, and the in-laws soon, though, and if I do, the card will get a real work-out! (DH has a ton of siblings.)
That actually raises another question. I know that the DDE card can be used for up to 10 people (I forget if that includes the card holder, or if it's 10 plus the card holder.) If all my in-laws and nieces and nephews go, that'll be like 16 people total. Can I get DH his own DDE card and then have the discount available for up to
20 people? I know that if you have DDE, you can get your spouse a DDE card for $25, but does that give each of you a discount for up to 10 people, and does the spouse have to be an annual pass holder? I have an AP, but DH doesn't -- he doesn't go to Disney nearly as much as I do. (Unlike me, he has a real job, poor guy!

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If no one knows here, I will post on the restaurant board, but I figured someone might just happen to know the answer.