Do marriage certificates expire?

Marriage certificates from the United States do not expire. A lawyer in New York cannot say for sure that there is no such thing as an expiration of a marriage certificate if that certificate was issued by a foreign country since the law of that country would apply. However, it does seem very unlikely that such a thing would exist.

Nope, marriage certificates don't expire. If he he was validly married he can only end it by divorce or death.

Marriage Certificates do not have expiration dates, they only terminate after "death do you part" (or upon divorce).