In the event of the death of a chiropractic licensee, or the legal declaration of the mental incompetency of the licensee to practice, the unlicensed heirs or trustees of the chiropractor must dispose of the practice within six (6) months. At all times during that period the practice must be supervised by a licensed chiropractor. The board will consider a petition to extend this period if it is submitted within four (4) months after the death or the declaration of incompetence of the licensee, including identification of any extenuating circumstances that will prevent compliance.