14 CFR § 63.15 - Duration of certificates.
(b) A flight engineer certificate (with any amendment thereto) issued under § 63.42 expires at the end of the 24th month after the month in which the certificate was issued or renewed. However, the holder may exercise the privileges of that certificate only while the foreign flight engineer license on which that certificate is based is effective.
(c) Any certificate issued under this part ceases to be effective if it is surrendered, suspended, or revoked. The holder of any certificate issued under this part that is suspended or revoked shall, upon the Administrator's request, return it to the Administrator.
(d) Except for temporary certificate issued under § 63.13, the holder of a paper certificate issued under this part may not exercise the privileges of that certificate after March 31, 2013.