The average person is in Orthodontics treatment anywhere between 18-24 months. For some people it'll be less time and for others it'll be more. It all depends on how much work needs to be done in your mouth. And remember, it's only an estimate. The only way you can keep your orthodontics treatment on schedule is by keeping everything nice and clean, not missing any of your appointments and by making sure you don't break any of your braces off. And of course, follow all your Dentist's instructions!
Any surgical or invasive procedure carries risks. Before proceeding, you should seek a second opinion from an appropriately qualified health practitioner.