Social perception has changed to where a person can decide to improve themselves at any age.  Provided that the teeth and gums are healthy, there is no age limit to orthodontic treatment. 

Other Benefits to Straight Teeth
1)  Improved chewing function
2)  More comfortable bite
3)  Less wear and tear on teeth and jaw joints
4)  Easier to clean -> Reduces tartar build-up and lowers incidence of gum disease.

Joint Treatment
We often work together with general dentists to improve the position of teeth for future crowns, bridges, veneers, cosmetic bonding, or implants.  If you are not certain if this applies to you, ask your general dentist.