Approval of the preliminary plat shall be effective for 12 months; except, however, the Board, upon written request of the subdivider and advice of the Administrative Officer, may grant an extension of time. If the final plat is not filed with the Administrative Officer within 12 months or authorized extension thereof, of the Council approval of the preliminary plat, all previous approvals of the preliminary plat shall become null and void. Submission of a current preliminary plat with construction drawings shall constitute an updating of the preliminary plat upon approval of the construction drawings.