Legal Question in Family Law in California

It depends. Every scenario is different but long term support does not have a definitive cut off date by law. The court has to have continuing jurisdiction to consider a modification/termination of support (unless either party dies, or the supporting party remarries). If they do the court looks to see if there has been a material change of circumstance in which the court should modify/terminate the award. The burden would be on you to prove that material change.

Post-Judgment modifications are often nuanced arguments. It is highly advisable for you to seek counsel.