I was 7 when my 9-year-old sister pointed out that it was funny how we got more/better presents from Santa when our rich uncle was visiting for Christmas... I had seen price tags on some presents before and was told that the elves had to buy items that were trademarked, patented, etc. I kept pretending until I was about 13 though, because I got presents from Santa and my parents at both my mom and dad's houses...I figured if they knew that I had it figured out, I'd get a lot less.
So yeah, I'm glad that I never caught my parents putting the presents out or anything... I don't think I could have pretended for so long if I heard my Dad telling me "Santa's not done yet!!!" ....although it's hilarious, or maybe it's just the way Munro says it that makes it hilarious...