Your mouth is dynamic and always changing and orthodontists like Dr. Song know this final phase of treatment is just as important as when you wore braces. Fortunately, it usually takes just 3-6 months to be completed, as described in these instructions.
Your retainer will be custom-made of a durable, but thin material so that it can fit into your mouth comfortably for 20-22 hours a day. Sometimes it takes a few days to adjust to the feel and to speak clearly.
But the thinness also means that it or the elastics can break if you do not treat them gently. If this happens, you will need to see Dr. Song ASAP to repair it (do not try to do this yourself, which can cause damage that cannot be fixed). Any delay can allow the teeth to start reverting to their original positions. If you fly, be sure to bring them in your carry-on bag, not leave them in luggage where they might be crushed. Also, avoid exposing the retainer to high temperatures, which could melt or warp it.