I was working 12-14 hours a day and coming home to take care of my wife, and then the wife and a baby. Two hours of sleep a night was a godsend. After a year of this, I was toast. Mentally, physically, emotionally, spiritually.
If I may ask-- what are you doing for work now? I have not yet answered this question.
One way to screen startups would be to see how founders and startup investors behave. I was greatly encouraged at LTSE by our CEO's example and saw one of our investors (Alexis Ohanian) publicly champion better and more sustainable work-effort and also take parental time off.
I think the worst legal behavior would be to demand 7 hours and 59 minutes of unpaid overtime per week. Past that, federal law steps in. So at worst you'd be working a tiny bit less than 48 hours per week... or you'd get paid more, which is a solid disincentive for the company.
Let's face it. Most startups are straight up toxic. Been there, done that. Never again.
On the flip side, though, if I saw a startup that enforced a proper work/life balance for their employees, while fairly compensating them with pay, healthcare, and clearly defined Vacation/PTO policies (none of that "unlimited vacation" bullshit trap that startups like to pull), and perks like 7 weeks of PTO for new fathers/mothers, then I would actually consider working for a startup like that.