"I need Mommy num-nums."
"I know you want num-nums, and I know you really like num-nums but maybe you don't need num-nums, now that you're such a big boy. Tell you what: you lie down in your bed and I'll go upstairs and tuck your baby sister in, and then I'll come back in 10 minutes to check on you, and if you still feel like you need num-nums you can have some in 10 minutes.
"Oh, I will need Mommy num-nums in 10 minutes."
"Yes, Mommy. Because I am a mammal."