Does weight matter when it comes to how long a baby can be EBF for?? DS is at least 18 lbs now and he's 4 1/2 months....during the day he's nursing every 1-1 1/2 hours. Sometimes he wants to nurse 1/2 hour after he has just ate. Night time he goes 4-5 hours without a feed...but it's really draining. So my question, does it matter how big a baby is when determining how long a baby can be exclusively breastfed.