Then it reaches its highest point, and begins to decrease. This is the basic peak pattern of crying in infants. However, although they all do it, there are lots of differences between one infant and another. For example, some infants might have their peak at 3 weeks of age, while others have it at 8 weeks of age. For some infants, the amount of crying that infants do at the peak might be 1 hour a day; for others, the amount of crying might be 5 hours.