When they reach the age where they think it's "not cool" anymore.

A lot of my friends stopped trick or treating in the 6th or 7th grade.... but I kept going until the 9th (or was it 10th grade?) grade because I liked it and it was fun.

Once I became a teenager, I used to go out with my little sisters or with other neighborhood kids that I babysat for, but I still loved getting dressed up and getting candy.... and the parents of the little kids I babysat for loved that I would offer to go with them because it was an extra set of eyes to help watch the kids.

So, I think that as long as the child/teen wants to trick or treat, and as long as they still have fun doing it -- then let them do it.

If you are worried about neighbors thinking it's 'weird' or neighbors actually saying something nasty about an older child or teenager trick or treating, then arrange to go with a group that includes younger kids.

My 2 cents.

Liz