For what period President and Members could hold the office

The President of the Appellate Tribunal shall hold office for a term of three years from the date on which he enters upon his office, or until he attains the age of seventy years, whichever is earlier and shall be eligible for reappointment The Judicial Member of the Appellate Tribunal and the State President shall hold office for a term of three years from the date on which he enters upon his office, or until he attains the age of sixty-five years, whichever is earlier and shall be eligible for reappointment.
The Technical Member (Centre) or Technical Member (State) of the Appellate Tribunal shall hold office for a term of five years from the date on which he enters upon his office, or until he attains the age of sixty-five years, whichever is earlier and shall be eligible for reappointment.

(ICAI FAQ PUBLICATIONS 06-09-2017 Qualification, appointment & condition of service of the President and the members of the Tribunal: FAQ NO. 35)