I agree, 10 hours is too long. I think the general advice for b'fed newborns is 5-6 hours once in 24.

A friend of mine had a newborn who'd sleep 6-8 hours every night from birth and lots during the day too. Let's just say that the b'feeding didn't work out. She had issues with low supply after a few weeks.

(PS Is there a tiny teeny bit of you that wants to scream because she's getting that much sleep?? LOL!)