Here's a tip for you that my parents experienced first hand...
If you have any unused, non-expiration park tickets left at the end of your vacation, make sure ONE person is responsible for all the unused tickets. Better yet, make sure that ONE person is someone who is organized and loves Disney.
My parents got the 4 day Military tickets in March and used one day. They planned to use the rest of their days this month. The night before they left, my mom asked my dad if he had his ticket and he said, "No. I thought it was my room key from March and threw it away at the end of our last trip..."
It stinks, but it can happen.