Every form of insurance document and every rate or other filing lawfully in use immediately prior to January 1, 1961, may continue to be so used or be effective until the Commissioner otherwise prescribes in accordance with this title, except that, before the expiration of one year from and after January 1, 1961, neither this title nor the Commissioner shall prohibit the use of any such document, rate, or filing because of any power, prohibition, or requirement contained in this title which did not exist under laws in force immediately prior to January 1, 1961.