17. Period of service.-
(1) Every person deemed to be enrolled in the Air Defence Reserve shall be liable for service-
(a) if he belongs to any of the classes specified in clauses (a) to (f) of sub-section (1) of section 11, until he has completed his forty-second year;
(b) if he belongs to any of the classes specified in clauses (g) and (h) of the said sub-section, until he has completed his fifty-fifth year.
(2) Every such person, on attaining the age specified in sub-section (1), shall cease to be a member of the Air Defence Reserve.