(a) The court may modify an order that provides for the appointment of a conservator of a child, that provides the terms and conditions of conservatorship, or that provides for the possession of or access to a child if modification would be in the best interest of the child and:
(1) the circumstances of the child, a conservator, or other party affected by the order have materially and substantially changed since the earlier of:
(A) the date of the rendition of the order; or
(B) the date of the signing of a mediated or collaborative law settlement agreement on which the order is based;
(2) the child is at least 12 years of age and has expressed to the court in chambers as provided by § 153.009 the name of the person who is the child’s preference to have the exclusive right to designate the primary residence of the child; or
(3) the conservator who has the exclusive right to designate the primary residence of the child has voluntarily relinquished the primary care and possession of the child to another person for at least six months.
(b) Subsection (a)(3) does not apply to a conservator who has the exclusive right to designate the primary residence of the child and who has temporarily relinquished the primary care and possession of the child to another person during the conservator’s military deployment, military mobilization, or temporary military duty, as those terms are defined by § 153.701.