The court generally reviews each case every six months, so the parents have that long to get through everything required of them, or as much as they can. The county helps parents do most of this. When the six months is up, the court receives reports from all the social workers, therapists, lawyers and others involved in the case, and decides whether or not the kids will be returned to their parents. If the kids are not returned, the parents are given another six months to do whatever is required of them. These attempts at reunification continue for up to eighteen months, after which if the parents are still deemed unfit, the court usually abandons reunification and recommends finding a permanent home for the children. This could involve long term foster care, termination of parental rights and adoption, depending upon the child.
All but two of my foster children were returned to their parents within eighteen months.