Waking up your baby to feed him/her

Heather
Baby Jasper is 18 days old. Went to our 2 week appointment last Thursday and I had mentioned to her saying we have to wake up the baby up every 3-4 hours to feed him. I was concerned, she said it was normal. She also mentioned that in a couple of weeks if the baby doesn't wake up on his own then just let him sleep and mom and dad can have their full night sleep as well. Thank goodness! So now I was discussing with dad we feed him one good time around 10 or 10:30 and he will wake up around 3 or 3:30... once. Other mom's had said if he sleeps just let him and if he is hungry he will let you know. What are y'alls thoughts on this?