Mich. Comp. Laws § 207.610

Sec. 10. (1) Unless earlier revoked as provided in section 9, a commercial housing facilities exemption certificate shall remain in effect for a period to be determined by the legislative body of the local governmental unit and commencing with its effective date and ending on the December 31 following not more than 12 years after the completion of the new facility. (2) The date of issuance of a certificate of occupancy, if one is required, by the appropriate municipal authority shall be the date of completion of the new facility.