My daughter was 10.5 yrs old when she got hers and wore them for 19 mths. Now she just wears retainers. My son was 13ish and still wearing them 18 mths later. He had 5 baby teeth removed as they weren’t falling out and one was stuck in his roof (oral surgery) so that one tooth is taking longer to get in line. The mask wearing for him at school has been perfect.