How long after dui (1yr ago) can mother regain primary caregiver in joint custody

Child custody is always subject to further review by the courts, even when there is a signed agreement. This is because it is about the children, rather than the agreement of parents. Neither the DWI nor the father's drinking are an absolute bar to custody, and so there is no set time limit to wait. They are just among the many factors that a court will take into account. This is very complicated area of law, and only a good domestic attorney in your state can give you the best chance to see it change.