Do you code for your day job, though? Your profile suggests you may be a technical manager. I'm guessing you don't code for 8-10 hours a day, then come home and code for 1-2 more hours[0]? That's the argument the parent is making. I know that I personally am only good for 4-6 hours of productive coding. Any more than that and I write bugs, not code.

[0]: If I'm wrong and you're doing 10-12 hours of productive code a day, then good god man, what's your secret?!?