According to Electronic Arts, "as a rule, no Online Pass should expire," meaning that the one-time use code shouldn't turn off after a set period of time. Despite this, some titles have had their Online Pass become non-functional.
Some games like EA MMA have simply removed the requirement of an Online Pass to play online. However, other games like Medal of Honor still require one and still have expired pass codes. The End User License Agreement (EULA) for Medal of Honor makes no mention of expiring codes, and makes no mention of the publisher's ability to cancel codes at any time. The EULA does state that EA has the right to terminate online services within 30 days of announcing it on its status page.
As it is, players who purchased Medal of Honor and Need for Speed: Hot Pursuit are still stuck with EA Online Pass codes that don't work.