Once your teeth are straight, it takes time for the bone and tissues to settle down and stabilize. It can take a year or even longer for these tissues to become fully stable and if your teeth were significantly repositioned, the time required might be even longer. When you stop wearing your clear aligners, the bone is still in the process of remodelling, unfortunately, teeth always follow the path of least resistance, so if nothing is holding them in place, your teeth are liable to move. If you were to merely stop treatment, they would gradually shift back to their original positions, but this is prevented when you wear your retainers.
Everyone needs a retainer immediately after a clear aligner treatment period. Whether you've had extensive orthodontic treatment to fix crowded and misaligned teeth, or if you've had shorter partial treatment, a retainer will keep your teeth from reverting to their original position.
If you wear clear aligners for 2 years, you may wear retainers for at least 6 years!. The exact time required to wear a retainer each day and period will depend on several different factors that include the complexity of your orthodontic treatment and your age. Your orthodontist probably recommended you to wear a retainer every day for many months. After this initial period, your dentist at Smile Centre India probably told you to continue wearing it for 3 to 5 nights a week for over a year.