This is the core of the problem: 'slack off' is actually 'having a life' but you yourself and everyone in the ratmill finds it slacking off. Maybe you are lucky and will realize that this is crazy before your health catches up.

That's not me.

Maybe it should be?

Don't see it as 'slacking off' though. See it as establishing a mature work/life balance.

The problem is that as a startup founder/CTO type the way you work sets the pace and culture for your entire company. And not everyone will be cool with that approach. You could miss out on experienced, senior people who just want to work normal hours and not feel like they're letting the side down.

I don't know you, but you get my respect for that statement.