The following are quotes from the section "Upgrades: Magic Your Way Tickets to Annual Passes" from the Cast Portal (updated 8/9/06). (Note - the first paragraph below is a paraphrase combining parts of two paragraphs and leaving the technical instructions out, the other two paragraphs are quotes.)
Because MYW tickets are configured to expire based on FIRST USAGE and Annual Passes are configured to expire based on DATE OF ISSUE, Cast Members must manually enter the expiration date to be one year from the original ticket's FIRST USAGE.
Guests are able to upgrade or modify their MYW tickets any time within 14 days of first use, regardless of whether the No Expiration Option is purchased. After 14 days no ticket modifications or upgrades may take place.
When upgrading to Annual product, of the Guest's original ticket included Water Park Fun & More Option, and any part of that option was used, then the Guest may only upgrade to the Premium Annual Pass.
Of course you cannot use more than one pass to upgrade to an Annual, it must be a one to one relationship only.
