(a) Except as provided by Subsection (b), the commission may not investigate and shall dismiss a complaint filed on or after the seventh anniversary of the date:
(1) the alleged misconduct occurred; or
(2) the complainant knew, or with the exercise of reasonable diligence should have known, of the alleged misconduct.
(b) The commission may investigate and not dismiss a complaint described by Subsection (a) if the commission determines good cause exists for investigating the complaint.