Conn. Gen. Stat. § 8-26g

(b) In the case of a subdivision plan approved on or after June 19, 1987, failure to complete all work within such ten-year period shall result in automatic expiration of the approval of such plan provided the commission shall file on the land records of the town in which such subdivision is located notice of such expiration and shall state such expiration on the subdivision plan on file in the office of the town clerk of such town, and no additional lots in the subdivision shall be conveyed by the subdivider or his successor in interest as such subdivider except with approval by the commission of a new application for subdivision of the subject land. If lots have been conveyed during such ten-year period, the municipality shall call the bond or other surety on said subdivision to the extent necessary to complete the bonded improvements and utilities required to serve those lots. “Work” for purposes of this section means all physical improvements required by the approved plan, other than the staking out of lots, and includes but is not limited to the construction of roads, storm drainage facilities and water and sewer lines, the setting aside of open space and recreation areas, installation of telephone and electric services, planting of trees or other landscaping, and installation of retaining walls or other structures.

(c) (1) Notwithstanding the provisions of this section, for any subdivision of land for a project consisting of four hundred or more dwelling units and approved prior to July 1, 2011, that has not expired prior to July 12, 2021, any person, firm or corporation making such subdivision shall complete all work in connection with such subdivision not later than the date nineteen years after the date of approval of the plan for such subdivision. The commission's endorsement of approval on the plan shall state the date on which such nineteen-year period expires.

(2) Notwithstanding the provisions of this section, for any subdivision of land for a project consisting of four hundred or more dwelling units and approved on or after July 1, 2011, but prior to June 10, 2021, that did not expire prior to March 10, 2020, any person, firm or corporation making such subdivision shall complete all work in connection with such subdivision not later than the date nineteen years after the date of approval of the plan for such subdivision. The commission's endorsement of approval on the plan shall state the date on which such nineteen-year period expires.