Originally Posted by VegasGambler

Physical mailer ones seem to be good at stated expiration + 2 months
Based on a couple of personal data points, emailed ones from AA seem to expire either on the stated expiration or just a few days after (I tried one at expiration + 1 week and it was no good, and a co-worker had a similar experience)

Note the change to emailed mailers (see question #3 in the FAQ) -- they appear to circumvent 24-month rules now if they contain a 9-digit code and come from AA directly.