A person appointed by the Secretary of State as a member of the Authority shall cease to hold office at the end of such period not exceeding three years from the date of the appointment as the Secretary of State may in making the appointment specify and in specifying such period the Secretary of State shall have regard to the desirability of retirement in rotation.

A person appointed under subsection (2) of section 4 (Constitution of Authority) of this Act shall cease to hold office at the end of such period not exceeding three years from the date of the appointment as the persons making the appointment specify at the time of the appointment.