I think you are too old to trick or treat when you hit the age of 12. We don't pass out candy at our house. We only have a couple kids in the neighborhood and they never stop by. Plus we are out with our kids anyway.
When I was a kid, I decided that after 6th grade I was too old for trick-or-treating. My kids are in 7th and 10th grades, and both plan to go trick-or-treating tonight. I roll my eyes and tell them at what age I gave it up, but don't forbid their participation.