Romeo sleeps like that sometimes, too. He sticks his tongue out a lot, it looks very funny.
When the kittens were little and Lilith was still cleaning them, she stopped in the middle of grooming one of them, with her tongue sticking out a good half inch or more. It looked like she was saying, "Feh! This kitten tastes gross!"
I just got online and saw your post It's not silly at all. I have about 5 of them who do it when they are relaxed or sleeping. The minute I start petting my Maine Coon, the tounge starts to pop out..LOL