This is commonly asked by mothers, as they feel that the baby should have a routine or pattern. However, it is best not to schedule feeding times, and force your baby in to a pattern such as every 3 -4 hours. All babies, but particularly those that are breast fed, should be fed on demand. Watch the baby for signs of hunger. All babies are different, but will soon get used to these signs. Such as rooting for the nipple, not settling and crying or whimpering sounds.
A baby can only hold about 1-2 ounces of milk in their stomach, so some may be hungry after an hour, while others may take a bit longer. If the baby has had a dirty nappy just after a feed, it is likely that he/she will become hungry sooner than a baby that has not had a dirty nappy. Usually within an hour of the feed.
It is also important to allow your baby to feed for as long as possible on one breast to ensure he/she gets the full benefits of the milk contents.
Ref: Breastfeeding and breast milk. Vital for our species - O & G, vol 9, no 3, Spring 2007, pp 38-40 Hogan M; Duursma L; Hansson D - (2007)