http://www.aa.com/vpupdate

Q3: How long are my systemwide upgrades valid?
A: Upgrades that were earned based on your 2004 flight activity are valid through February 28, 2006. Upgrades earned based on your 2005 flight activity are valid through February 28, 2007. In other words, the earlier in the year that you qualify or requalify for Executive Platinum membership, the longer you will have to use your systemwide upgrades. All travel using a systemwide upgrade must be completed by the expiration date.