Your permanent retainer will help to keep your teeth in the proper position, so is a wise choice. Although you feel your thumb sucking may have caused the gap between your teeth and you no longer have that habit, orthodontic relapse can happen when retainers are not worn...hence, orthodontic retreatment as an adult to fix the previously corrected problem is quite common. Enjoy your beautiful, straight, non-gapped teeth and believe your orthodontist has your best interest in mind with your permanent retainer!