“Certification period” means the period for which households shall be eligible to receive benefits. The certification period shall not exceed 12 months, except that the certification period may be up to 24 months if all adult household members are elderly or disabled. A State agency shall have at least 1 contact with each certified household every 12 months. The limits specified in this subsection may be extended until the end of any transitional benefit period established under section 2020(s) of this title .