Every permission for development granted under section 49 shall remain in force for a period of three years from the date of such permission:
Provided that the appropriate planning authority may, on application made in this behalf before the expiry of the aforesaid period, extend such period for such time as it may think proper; but such extended period shall, in no case, exceed three years:
Provided further that any expiry of permission shall not bar any subsequent application for fresh permission under this Act.