Any certificate issued pursuant to this chapter that has not been used by the holder during the 2-year period prior to the effective date of this section lapses on the effective date of this section. Any other certificate issued under this chapter, other than a certificate for the transportation of mail, that is not used within 2 years after the date of its issuance lapses 2 years after the date of its issuance. Any certificate issued prior to the effective date of this section for the transportation of mail that is not used within 5 years of the date of issuance lapses 5 years after the date of its issuance.   [PL 1991, c. 774, §4 (NEW).]