If your baby is sucking well during his feeds he may be getting a lot of milk in 15 minutes. If he's sucking efficiently it should be suck, pause, swallow. My baby often only eats for 3-5 minutes but gets plently of milk in that time. She is 3 1/2 months old and almost 15 pounds. I wouldn't worry about how long he's eating for as long as he's satisfied after feeds and having wet and soiled diapers every day.
