L.K.
My son is 11 months old. I use smaller bottles with him (4-5 ounces). The doctor told me he should take up to 28 ounces per day. If your son is growing well, I wouldn't worry about whether or not he finishes a bottle. Let him decide. The bottle in the crib is really convenient but can turn into a bad habit, especially if he starts using the bottle for comfort and wants to sleep with it. (It's bad for his teeth).