My 11-year old still believes and I'm fine with it.

My oldest (also an Aspie) is 10, turning 11 in December and still believes. He has even gotten into arguments with classmates over it. Funny thing is my husband is a Children's entertainer who is Santa over the holidays. When the children were younger they were clueless that it was him in the Santa Suit but as they got older they recognized his eyes and began to question it. We told them that Santa couldn't be every where so he hired people to help and that Daddy is Santa's Helper. So now when he's old enough to know the truth he still tells everyone Santa's real because he pays daddies pay checks and if Santa is real all the others must be too right. I think let him believe as long as he wants and show Polar Express when needed.