Texas Estates Code - EST § 751.131. Termination of Durable Power of Attorney

(1) the principal dies;

(2) the principal revokes the power of attorney;

(3) the power of attorney provides that it terminates;

(4) the purpose of the power of attorney is accomplished;

(5) one of the circumstances with respect to an agent described by Section 751.132(a)(1), (2), or (3) arises and the power of attorney does not provide for another agent to act under the power of attorney;  or

(6) a permanent guardian of the estate of the principal has qualified to serve in that capacity as provided by Section 751.133.