How Old is too old for Costumes?

Seriously, How old is too old for a child to be out in a costume trick or treating?

Cause, I'm pretty sure that once you have become a "teen" you shouldn't be knocking on ppls doors expecting candy.  WTF, Am I wrong here to think this way?

Last year I remember we had a group of "older" kids come by, well after the time that most kids would still be out. We of course did not answer the door. You say, well was your light on? Yes it was, but we leave our porch light on every night. In my opinion after 10pm is too late for any age of kid to be out knocking on ppls doors. None the less expecting to get candy!

I mean seriously WTF!

If you don’t answer the door, there is a good possibility that something will happen to your house. I know this isn’t very positive thinking, and might seem a little paranoid. But they are "teenagers" after all and they can be very destructive if they feel the need to be.

So anyways it kinda ruins the enjoyment of seeing all the young children that are dressed up and deserve to be out trick or treating when you have a group of older children show up. Sometimes not even in a costume. What do you say to those older kids that show up and are mixed in with the young kids that deserve the candy, without scaring the small children of course?

On a whole different note. I am a supporter of dressing up your animal for Halloween.
I also think that everyone should have doggie snacks as well for those dogs that trick or treat. Cause I know when we have taken our dog around, he had the best time going up to the door, waiting for "his" treat.
(yes,  my dog did have a costume on and he is under the "teen" age).