#0 - July 25, 2008, 5:50 a.m.
These promotional codes will apply only to the Wrath of the Lich King beta. The latest date to register the codes for the current round of beta invitations is Friday, August 1. Codes registered after this date will not be eligible for beta entry until a later date, so we encourage everyone to register early and be part of the vanguard into Northrend.
http://forums.worldofwarcraft.com/thread.html?topicId=8202577367&sid=1