The Commissioner of Administrative Services shall specify, at the time any candidate list is promulgated, the period during which such list shall remain in force. In no case shall a candidate list remain in force for a period of less than three months or more than one year, except (1) such period may be extended not more than two years by the commissioner as appropriate based upon the needs of the state, and (2) candidate lists for continuous recruitment examinations shall be based on the needs of the service.