There is no set time for a child protective proceeding to be closed once the court takes jurisdiction over the child. The court may retain jurisdiction even after the child has been returned to a parent, regardless of whether that parent is a respondent or not. You will need to discuss the specific facts of your case with an attorney that is experienced in child protective proceedings.
DISCLAIMER: This answer is provided as general information, which may not be appropriate for the specific facts of your particular situation. No attorney-client relationship has been established based on this limited communication. You are advised to consult with an attorney in your jurisdiction before taking any action or inaction that may affect your legal rights. www.hecklerlawoffice.com
I just want to add, in addition to what Ms. Heckler has stated, that the court might not think the father will provide a good home for the children if he lives in the home the children were taken out of, even if he was not doing drugs or anything illegal. Often when one parent is behaving badly, the other parent is perceived as endangering the children when they don't remove the children from such an environment. He may have to go through court-ordered steps to prove that he will provide a safe home.