All questions of fact and law and all matters submitted to the judges of the Tax Court shall be disposed of and their decision filed with the court administrator of the Tax Court within three months after such submission, unless sickness or casualty shall prevent, or the time be extended by written consent of the parties. No part of the salary of any judge of the Tax Court shall be paid unless the voucher therefor be accompanied by the judge’s certificate of full compliance with the requirements of this section. A Tax Court judge shall devote full time to the duties of the office and shall not engage in the practice of law.