How old is Too Old for Trick or Treating

Let's face it, trick or treating is a blast! First you rush through the drama of figuring out what to be for Halloween, then you spend hours putting together the perfect costume, applying make-up, teasing your hair (or hiding it under a wig!), and then, you grab a sack or bucket and head out the door to canvas the neighborhood for delicious treats. But, the lingering question looms, At what age should you call it quits?
I have a confession to make, the last time I went trick or treating I was 17 years old. In all fairness, I convinced my (then) boyfriend and his best buddy that Trick or Treating was far more fun than smashing pumpkins and egging houses, the more common choice of fun amongst teens in our area. I hadn't been trick or treating in a few years before that (since I was 13).
While most people were gracious and happy to see trick or treaters at their doors, I have to admit that I did get a couple of, "aren't you too old for this?", "Halloween is for little kids". The negative comments were more than enough to shame me into never going again. When you're little and you knock at the door, you're greeted with smiling faces who comment on how cute or neat your costume is, as you get old, you're often greeted with raised eyebrows and skeptical glances.
Although I have long since given up trick or treating, I find myself presented with the same question this season as my own sons excitedly ask, "Can we trick or treat this year?" What do you think the cut-off age for trick or treating should be? Give Your answers in comments.