S.D. Codified Laws § 36-6A-4
No member of the board may serve more than three consecutive full terms. However, appointment of a person to an unexpired term is not considered a full term for this purpose. The Governor shall make appointments to the board for terms of three years. Each member shall hold office until a successor is appointed and qualified. The Governor shall, by appointment, fill any vacancy for the balance of the unexpired term. The Governor may stagger terms to enable the board to have different terms expire each year.
The terms of members shall begin on October thirty-first of the calendar year in which the Governor appoints the member, unless otherwise designated by the Governor. The appointee's term shall expire on October thirtieth in the third year of appointment.
SDCL 36-6A-4