Unfortunately, you have to use your tickets within 14 days of the first use.
Just a note.
Although that info is basically correct
(tickets, after they have begun being used, do expire within a few days)
the blanket rule of "within
14 days" is no longer entirely true.
Since Disney started using "date-based" tickets, the amount of time that unused days remain valid is now based on the number of days that where purchased on the original ticket.
In fact, most tickets expire in
fewer than 14 days.
Examples: (Base or Park Hopper Tickets)
2-day tickets expire within 4 days of first use.
4-day tickets expire within 7 days of first use.
5-day tickets expire within 8 days of first use.
8-day tickets expire within 12 days of first use.
10-day tickets expire within 14 days of first use.