Here is the email I got back regarding using them next year:
Hello Beth,
Thank you for contacting the Universal Online Ticket Store. The 2
park unlimited pass does not have an expiration date. You may start to use
these tickets at anytime. However, the ticket is valid for 7 consecutive
days, starting with the first day of use.
If you should need additional assistance, please let us via email
or you may contact an Online Ticket Store Representative at (407) 224-7840.
Representatives will be available Monday through Friday 8 am to 10 pm EST
and Saturday through Sunday 9 am to 8 pm EST.
Kaiwana
Universal Online Ticket Store