Ok I know this sounds like a dumb question but if you do it by demand how do you know that its a bottle they want. If they don't take it do you put it in the fridge for later. My problem is not that he's wanting to feed more than every 4 hours but he doesn't want to feed, because he's busy playing at his play times. He seems so excited to see his bottle but very very quickly loses interest in it and what's to be put down again.