Sleepover

I'm realizing there are a few problems with having "big kids" and "little kids". The biggest problem - the little kids think they are big kids:

Lizzy: "Mom, can I have a friend sleepover tonight?"
Me: "Nope. Not tonight."
Lizzy: "Why? Lexi has friends sleepover all the time!"
Me: "Um, Lexi is 12. You're four."
Lizzy: "Fine, when my 12 my can have sleepovers every night?"
Me: "Ok."
Lizzy: "Wait... Lexi had sleepovers when her was 11."
Me: "Ok, you can have a sleepover when you're 11."
Lizzy: "Fine... like 300 sleepovers!"