@Sierra how do you keep the milk nearby ready? Is it formula? Do you batch pre make and warm up when he needs it?
@FTM when I pump I leave it out at room temp. It's good that way for 4-6 hours Even if you take it out of the fridge it can be out for an hour and still be refrigerated again ask I would just leave it near me and put it back as soon as he's done
What we would do (still do) is keep the milk nearby but only fill the bottle with how much i know he'll take (in your case 4oz) and if he wants more just pour one more oz at a time so at most you're wasting 1oz or less depending on how much he eats. We typically give 3oz and top up 1oz at a time when he needs it, up to 5 or even 6oz if he's hungry