DCA-IAH is one of the toughest upgrades in the system and is notorious for having all seats held back from EUA. In my experience as a Gold, the only DCA-IAH flights that have even a remote shot at a normal EUA (i.e., at the upgrade window of your elite status) are the early morning flights. I've been on DCA-IAH flights that have showed A9 D9 Z9 etc. and had totally blank seat maps the morning of departure (or only FAM seats blocked and A9 D9 Z9 etc.). The GA's usually process the remaining upgrades at the podium before departure - if you get upgraded, it won't be until the airport.

With respect to what others have said regarding GA's giving away their battlefield upgrades when the passengers weren't at the gate to claim them, I wonder what CO's policy is with respect to the amount of discretion GA's have in processing upgrades? It would make sense if the policy were to wait until boarding is nearly complete and if the original upgraded passenger still hasn't arrived, to battlefield the next person on the list rather than just upgrade someone else if the original passenger is not at the gate the first time his/her name is called. GA's should not be permitted to simply call off names and skip passengers who happen not to be at the gate at the time their name is called.