The answer to this frequently asked question is……As long as you want your teeth to stay straight.
Regardless of what type of orthodontic treatment you received; a retainer was more than likely included in the orthodontic fee. Why risk the chance of your teeth returning to their pre-orthodontic position; wearing them regularly will prevent this.
Teeth have history. It normally takes about a year for the teeth to become stable in a new position. Therefore, retainers should be worn for at least 22 hours a day, right after braces are removed. After 3-4 months, when your orthodontist feels your teeth are stable, you will be instructed to wear your retainers at night, every night; while you sleep. If after a few months your teeth are stable and no movement is seen; you will be instructed to wear your retainers just a few nights a week; FOREVER.