(1) The period of enlistment in the Washington state guard shall be set by regulation by the adjutant general or the adjutant general's designee.

(2) Notwithstanding subsection (1) of this section and RCW 38.12.180(2), the adjutant general, or the adjutant general's designee, may extend the service age upon request by an active member of the Washington state guard if the adjutant general, or the adjutant general's designee, determines the member's extension would be in the best interest of the Washington state guard. Extensions under this subsection have a two-year duration and may be renewed beyond the age of sixty-four, subject to the discretion of the adjutant general or the adjutant general's designee, if:

(a) The member is physically and mentally capable to complete all assigned mission tasks; and

(b) The Washington state guard officer review board recommends the extension.