After looking at my code leaflet for Mogu Mogu earrings there appears to be no expiry on it however please note the item code is region locked (and is the only region locked code since launch) it would be best to use email support to see if they are still offering code exchange for other regions than Japan.

Link to post about code exchange
http://forum.square-enix.com/ffxiv/t...=1#post1234578