So, when do you all think it's too old for a child to go trick or treating? I'm just trying to figure out when that age would be.
I use Hallowe'en as a way to encourage artistic expression in my children. As they grow older, I continue to encourage them to dress-up and I model this by accompanying them in costume. However, as they grow older, the focus changes from them being the ones asking for candy to them creating more elaborate costumes and being chaperones for the little ones who do the asking, and if the resident is generous with them too, bonus!
The older the children are, the more effort I expect in their costumes. How often do you see works of art paraded to your door? Teenagers who present themselves as skateboarders are asked to do tricks or are turned away with the suggestion that they try harder next year. Other times, because teenagers are often the ones who knock later, my kids get to answer the door and see the kinds of costumes and transformational make-up masterpieces to which they can aspire. I do not have a problem trading candy to see that! Some kids don't even ask for anything, they just do their magic tricks or read their poems and wish us a happy Hallowe'en.
So, to answer your question, I think a person should stop going trick or treating when they no longer put age-appropriate effort into their costumes or when they aren't prepared to give something valuable in exchange for their treats.
I think that a child will make it clear that they would rather go to a Halloween party than to trick or treating. Having seen engineers and artists, and artistic engineers, creating some fantastic costumes, I don't think that there's an upper age limit on Halloween - even the dead and undead can be found at such parties.
Simply put, I think your child will let you know when they don't want to do the same thing and want to do something different, such as a party, a haunted maze, or some other activity.
At some point, you might find it interesting to introduce them to something quite different, such as Dia de los Muertos or a Halloween-inspired organ performance.
My view is they are too old, when they decide they are.
We get a wide range of kids, although we don't give candy away - neither my wife and I really like to encourage that sort of thing, more importantly we get a small amount of treaters due to the location of our street. Buying candy means we'd eat most of it after, so we give away small decks of playing cards, or small containers of Play-Doh. When I took my son out we saw quite a few teens out dressed up, some were imaginative and other's just had on head bands with springy things on top.
Personally I'd rather have nGinius' neighbors, but we get a few well decorated houses (mine is slowly getting there) and often the kids and parents dress up similarly so it's like a roving party.
I find myself far less concerned with the older kids trick-or-treating than the parent with an infant who clearly should not be having candy coming to the door to get their candy.
I think a long as there is effort in dressing up and their are respectful, there is no problem with older kids going out. I do expect a thank you though and call kids out on it if they fail to say thank you!