Did this a few years ago. Took a little under 2 years to straighten my bottom teeth that I always hated. My parents never bothered or didn't have the money. I was over 40 and did it and just love the result!
Made me feel better about my teeth and got a lot of compliments. Not easy to do taking the trays in and out of my mouth when you have to eat, carrying a tooth brush around all the time but in the end it was well worth the time and money!