Can you ever spend too much time with an infant?

A guy I know has a baby daughter. He and the mother of the child are not together. He works 16-hour days, and the time he’s not at work, he’s with his daughter. Only when it is extremely necessary does he leave her with a grandparent or another relative (e.g. working, going to the store, etc.) Other than that, he does nothing for himself. He doesn’t hang out with his friends or do the things he used to enjoy.

Do you feel this is an issue?
Should he “lighten up”?

I’ll post my opinion soon.