As a retired Superintendent (really, as a retired administrator) *anyone* can work up to but not exceed 2 years in any one district. In accordance with NJ pension regulations, any retired superintendent (or retired assistant superintendent, or retired principal, etc..) can work up to but not exceed 2 years in any one district but are not limited to going to another district once their "term limit" is up. These rules are established by the NJ Pension system and are intended to allow district to hire "temporary" people in key roles until a permanent position is filled. State pension statutes place a two-year limit on the length of time a retired superintendent can collect a pension while earning a salary as an interim superintendent.
Not all retired educators are eligible for this provision. Former teachers who return to the classroom must cancel their retirements and re-enroll in the pension fund. This happened following the repeal in November 2003 of a rule permitting interim employment for up to six months without penalty. Exempted from that decision were certified superintendents and administrators, including principals and school business administrators, who already were playing by a different set of rules. Starting in January 2002, retired superintendents and business administrators were permitted to accept employment on an interim basis for up to two years in a single district. With just a small break between jobs, retired superintendents can hop from district to district without affecting their pension income.
It's not clear if Hoboken interim superintendent Carter would have wanted to serve another year or if the Board of Education would have wanted him to serve another year. But, as a retired employee serving as an interim superintendent with less than 1 year of tenure in a single district, he was legally able to serve an additional year.