Can I add days onto my theme park tickets?
Yes, park tickets can be modified through the My Disney Experience app or by calling your travel agent. If a ticket is changed to a higher priced time period, the guest is responsible for paying the difference in price. If the guest changes to a lower priced period there will be no refund for that. If a ticket needs to be changed after the start date, guests can visit any Guest Relations location at Walt Disney World.
Exceptions – no Disney World ticket can exceed 10-days. If adding additional days would make the total go above 10, you cannot do that. You can add on extra days as many times as you want, as long as the total number of days never exceeds 10. Park Hopper Plus Option entitlements are not counted in the 10.