How long is my building permit good for?

The Massachusetts State Building Code stipulates that any permit issued shall be deemed abandoned and invalid unless the work authorized by it shall have been commenced within 6 months after its issuance; however, for cause, and upon written request of the owner, 1 or more extensions of time, for periods not exceeding 6 months each, may be granted in writing by the building commissioner. Work under such a permit in the opinion of the building commissioner, must proceed in good faith continuously to completion so far as is reasonably practicable under the circumstances.