OK, here it is. Rather long but important! As per Allears:
ADDING DAYS TO MYW TICKETS
Effective with the price increase of February 23, 2014 Disney has changed it's policy on adding days. They will no longer add additional days on tickets that were not purchased from Disney. Those non-Disney tickets can still be upgraded to annual passes but you can no longer add any additional days to the ticket.
MYW tickets purchased from Disney can have days added to the ticket. You must add the days within the 14 day from first use window and you must have at least one unused admission remaining. No ticket can exceed a total length of 10 days. If you have a 10 day and used 5 days from it, you cannot add another day to it as the total cannot exceed 10. But if you have say a 7 day ticket and you use 2 days, you can add on up to three additional days.
Between January of 2005 and August of 2006, you were allowed to add days and options to any ticket that had no expiration on it. The policy was changed in August 2006 so that changes are no longer allowed to any ticket past the 14 day from first use window. Your unused park admissions remain valid. You just cannot alter the tickets in any way. Disney can do this because allowing the changes was a policy, not a condition of sale. It is the same situation as if they discontinued an Annual Passholder discount at one of the stores/restaurants where it has previously been offered. As long as the unused park admissions remain valid, they can pretty much do anything they want.
There is no limit to the number of times you can upgrade the ticket (as in adding only one day at a time each time you upgrade) but in all cases, the total admissions cannot exceed 10. Park Hopper and Water Park Fun & More add ons do not count in the total. All upgrades must be done prior to or within 14 days of first use of the ticket and the ticket must have at least one admission remaining.
Depending on where and when the upgrade is performed, a new ticket may or may not be issued. Typically, a new ticket is issued if it is upgraded in a system different from its original issuance media (i.e., resorts stock, paper stock at the parks, etc). Regardless if a new ticket is issued, the original biometrics information will follow the ticket through upgrade.
ADDING ON OPTIONS TO MYW TICKETS
Effective with the price increase of February 23, 2014 Disney has changed it's policy on adding options to tickets purchased from sources other than Disney. They will no longer add park hopper or water park options on tickets that were not purchased from Disney.
Disney allows you to add on any of the available ticket options to an already purchased or even a used MYW ticket provided it was purchased from Disney. The add ons available are the Park Hopper option allowing visiting multiple parks on the same day, the Water Park Fun & More option which gives a varying number of visits to the water parks, DQ, or WWoS, and the no expiration option which will make all your unused admissions, both theme park and WPF&M options, never expire.
These add ons are done on a fixed cost basis. That means if you have a 7 day MYW Base ticket and you decide to add the park hopper add on for the last three admissions remaining on the ticket, you will pay the full $ 60.00 + tax to do it, not a prorated amount. This holds true for all of the add ons including no expiration. They are all a fixed price based on the original length of the MYW ticket, not what's left unused when you do the transaction. The price is never prorated.
The no expiration option must be added within 14 days of the first use of the ticket. You can even have used park admissions before doing the add on. No expiration can only be done in person at WDW or with tickets purchased from an official Disney wholesaler. The add ons can be done at any Guest Relations location at the theme parks or at DTD as well as at any Lobby Concierge location at a Disney resort. Note that Lobby Concierge cannot do any transactions involving AP/PAP/SP's. The Park Hopper and Water Parks Fun & More options can be added at any time within the 14 day window.
EXCHANGING OLD CHILDREN'S TICKETS
Many people find themselves in the situation of going to WDW with their young children and having unused days left on their tickets when they return home. These tickets are put away, often for many years, until another trip to Disney is planned. But what can you do with these tickets since your then child is now a teenager or even an adult and obviously can't use a child's ticket now?
What you have left will depend on how this transaction is handled. If you have a brand new, completely unused child's ticket that you bought years ago you will only be able to apply a dollar value equal to the price you paid for that ticket towards any new adult ticket that exceeds the price of the old one. This is your only option with an unused child ticket.
But if you have a partially used ticket, you may take that ticket along with your child who is now a teenager or older to a Guest Relations location at the major parks or DTD. If the Guest Relations CM is satisfied that the dates of the original ticket and the current age of your child make sense, you will have the leftover child's admissions exchanged for the identical adult admissions at no further charge to you. The "child" must be with you or you will be unable to do this.
Making sense of the dates means that if you bought and used the child ticket in 1998, then your child in 2008 must now fall in the 13-19 year old range. If you bought and used it in 1988, then the "child" must now be in the 23-29 year old range, etcetera etcetera. If they are not, then Disney reserves the right to offer you nothing more than the dollar value of the unused admissions towards a new adult ticket.
A note on this: if your child is now 10, 11 or 12 years old, you can continue to use the old child's ticket as is and have no problem at the gate. The only time that you may run into a problem is when you have an older teen trying to use it. That is when you should exchange the child's ticket. Don't bother going to Guest Relations for an 10, 11 or 12 year old, just use it as is.
WHAT YOU CANNOT UPGRADE OR EXCHANGE
As a general rule, you can no longer upgrade previously used pre-2005 tickets. Tickets not available to the general public (such as band passes, sports tickets and some convention tickets) can not be upgraded to a regular MYW pass or AP/PAP. Also any pass that has a expiration date such as the occasional Canadian special at-par passes can not be upgraded or exchanged for credit on a pass with no expiration such as a regular MYW hopper pass. And of course, complimentary or free tickets (including the "Touch of Magic" tickets many time share tours give out) cannot be upgraded.
Effective August 3, 2011 any multi-day ticket may only be upgraded while there are still unused entries remaining. Example: if you have a five-day ticket and have used all five days, you cannot upgrade the ticket even if you are still within the 14 days from first use window. For a one-day ticket such as a one-day MYW or one-day water park ticket, any upgrade may be done only on the date of use. Florida Resident Play 3 and Play 4 tickets can still be upgraded within six months of date of first use.
WHAT IF I FORGOT TO ADD DAYS OR OPTIONS OR UPGRADE MY TICKET AND I HAVE ALREADY RETURNED HOME?
You must make the changes in person at WDW, depending on what you are doing either at a Guest Relations location or at the Lobby Concierge desk at your Disney resort. You cannot do it on the phone, online, or at a
Disney Store. It is possible to contact Disney Ticketing and on their instruction, mail them your ticket and a check for what you want to do. This is the only way to upgrade a ticket after you have left WDW. The 14 day window still applies even in these cases.
-On all upgrades, you will be charged the current gate price on the new ticket as long as at least one admission has been used on the old one and the 14 day window has not passed.
-Sad as it may sound, all Guest Relations CM's are not alike. Some are more capable and ambitious than others. If one tells you that you cannot do these transactions, go see another GR CM or ask for a supervisor.
Side note: It is possible that there could be new policies instituted by Disney in regards to handling upgrades and dollar credits of old tickets. Their entire ticketing policy has changed radically over the past two years and continues to be very fluid. Lately, every price change had brought more fine tuning with the upgrade policy.