My daugher was full term and late by two days. She slept a 95% of her first month..Her pedi was concerned because she would go long hours with out eating.. there was some talk of "Her system shutting down" because she slept so much and ate so little she "Did not have the engergy" to stay awake.. They put me on a schedule to where she had to be woken up every two hours to eat.. eventually it evened out and she is a healthy active three month old. If i was you..i would let the baby sleep no more then three hours with out eating.
My twins were born at 36.6 weeks and I was feeding them on schedule but they started to not want to eat so I tried out feeing them when they wake up and it's been going great there gaining more weight then when I had them on schedule the dr told me to keep it up and the midwives but I don't let them go to long without a feed a make sure it's still in good time. But if there small I'd monitor it to make sure there getting eveything they need even get advice off whoever is monitoring like the dr or midwife