Babies will stay on the breast for 2 hours because they like to suck

Most babies who stay at the breast for a long time are probably hungry, even though they may be gaining well. "Being at the breast" is not the same as "drinking at the breast". Latching the baby better onto the breast allows the baby to nurse more effectively, and thus spend more time actually drinking. Babies younger than 5-6 weeks often fall asleep at the breast because the flow of milk is slow, not necessarily because they have had enough to eat.