I believe it is 3 days. I am doing the same thing. There is a sticky with information on tickets and I found it there.
I. Picking up Package Tickets Prior To Start Of Package
In cases where Walt Disney World Resort Guests would like to begin using their Package Tickets prior to the day of check-in (up to three days in advance), the Guests will be directed to visit any Theme Park Guest Relations location and request Early Ticket Pick-Up.
It is only valid for people with packages at a Walt Disney World owned and operated Resort. You can be staying off-property at the time you pick up the tickets. Note that if you have a package which includes Dining, although you can pick up your tickets early you cannot get access to the Dining until you have actually checked in to your Resort.
There is a possibility that if your package and the stay prior to the package are at the same Resort that you will be able to get the tickets at the Resort and not have to go to a Park Guest Relations Office.
And the tickets issued will be valid for the entire stay; they will not receive valid tickets when they actually check-in to their resort. There is a strong possibility that the tickets you have received prior to check-in cannot be added to your KTTW on or after check-in.
http://www.disboards.com/showthread.php?t=1452684
