My son just turned four, and we still use "Yes" and "No" pretty regularly. It never would have occurred to me that you could sign "no" snarkily, but my son manages it.
Another interesting thing I've noticed is that I can recall the signs for things even when I'm tired and losing words. My wife and I were hosting a party and I'd run myself ragged. I was tired, exhausted and needed to sit down, but first our son needed some food. He'd asked for goldfish crackers. My wife encountered me as I battled my way to the kitchen and she asked me what I needed. I struggled to speak but no words came to mind, so I signed "Little boy wants fish crackers."
My wife replied with sign "You sit, I'll feed boy."
I went back to the couch and sat next to my son. He looked at me and signed "Where cheese fish crackers?"
I signed back "Mommy" and "wait."
He signed "OK," popped his thumb in his mouth and snuggled up to me while we waited.
My favorite use of ASL these days consists of side conversations. Not long ago my wife and I had a friend over. My wife and our guest were having a conversation in the living room, and my son was sitting around listening. I use ASL and asked him if he wanted a hot (grilled) cheese sandwich for snack. He said yes, and he wanted strawberries and milk. I went off to put together his snack and our guest started laughing.
"You just had a whole conversation with him, didn't you?"
"Yes."
