Section 183.15 - Duration of certificates(a) Unless sooner terminated under paragraph (b) of this section, a designation as an Aviation Medical Examiner or as a Flight Standards or Aircraft Certification Service Designated Representative as described in §§ 183.21 , 183.23 , 183.25 , 183.27 , 183.29 , 183.31 , or 183.33 is effective until the expiration date shown on the document granting the authorization.(b) A designation made under this subpart terminates:(1) Upon the written request of the representative;(2) Upon the written request of the employer in any case in which the recommendation of the employer is required for the designation;(3) Upon the representative being separated from the employment of the employer who recommended him or her for certification;(4) Upon a finding by the Administrator that the representative has not properly performed his or her duties under the designation;(5) Upon the assistance of the representative being no longer needed by the Administrator; or(6) For any reason the Administrator considers appropriate.Doc. No. FAA-2007-27812, 73 FR 43066, July 24, 2008