The American Academy of Pediatrics puts out an ADHD treatment guideline. The current version is from 2011. There is nothing about taking adolescents off medication. The closest it comes to that is saying that dosage may need to be adjusted periodically for all kids to maximize benefits and minimize side effects.
A CDC summary.
https://www.cdc.gov/ncbddd/adhd/guidelines.html
The full guideline is here.
http://pediatrics.aappublications.org/content/128/5/1007