I was 13 or 14. I stopped because my best friend was no longer trick-or-treating and because I was tired of hearing passive aggressive comments from the houses about my being tall, insinuating that I was too old to have innocent fun - should I perhaps have been out causing mischief instead, I wondered? Would they prefer to receive a "trick" over letting me cling to a favorite childhood activity by giving me a "treat"?
This is not to imply I was out for revenge. I never once harmed a house. But it seemed (and still does) a bit hypocritical to me, that the same adults who were always worried about teenagers behaving on Halloween also wanted to keep said teenagers away from an activity that would keep them out of trouble and let them retain a bit of childlike innocence for at least one evening.
All to say that while I stopped then, I actually started again last year! Unintentionally, but I was walking two young girls around when one wanted to return home. The other was so disappointed that I threw on a quick costume and went with her. And had fun! As people always say, Halloween is a time when you don't have to be yourself. For me I see Halloween as a time when it's acceptable to be childish and nostalgic and joyful. If someone wants to dress up and run through the night to knock on doors and collect candy because it gives them a giggle or a thrill, go for it - no matter what the age!