How long the teeth need to be held in place with retainers after alignment depends on the patient’s age, the type of initial malocclusion (how the teeth were out of line), the bite and the treatment method (expansion, moving the teeth back, or extractions). As a general rule, some authors advise that retention should last twice as long as the treatment, or at least 2 years after the end of active orthodontic treatment. There are cases in which we tell the patient right at the start that the result will need to be retained for life.
This answer is for general information. Your own case needs an examination by an orthodontist.