Unless a building permit or a certificate of occupancy authorizing construction or the use or occupancy of any premises in accordance with the terms and conditions of any variance, conditional use or site plan approval granted by the Board of Adjustment or Planning Board has been issued within six months after the date of the adoption of such resolution or within six months after the effective date of this chapter, whichever period shall last expire, any such variance, conditional use, or site plan approval shall expire, and before the use or occupancy permitted thereby may be commenced, a new variance, conditional use or site plan approval shall be obtained.