At night, I was told that there is no reason why your baby cant sleep for several hours at a time, there is no need to wake a baby every 2 hours in the night. Every baby is different and every baby will develope their own sleeping/eating habits. It also depends on how developed your baby is, remember, every baby developes differently in utero and is born this way too.
Your baby will know when they are hungry and you will be able to tell how healthy he/she is by weightgain, alertness etc. That being said, if it was getting onto 4 or 5 hours, I might wake the baby up.