I found it wasn't really the time that was a problem, it was attention. Even when I was at parties or with my families, I wasn't really mentally there, since there was always this cool algorithm or new approach that I was turning over in my head and wanted to try out. That tended to make parties not all that much fun for me, and me not all that much fun for the party. So even though I was only working 5-6 hours/day of actual coding, the mental effort spent thinking things through was all-consuming. It was depressing enough that I'm going back into the corporate world again - I'm not much of a work/life balance guy by nature, but I'd like more work/life balance than I had as a founder.

FWIW, none of the startup founders I know have much in the way of work/life balance, at least for the first 5 years or so of the company's life. It was not uncommon for them to work 12 hour days, 7 days a week, and take their first vacation when the company was about 4 years old. This doesn't mean it was a daily grind - just that their life became the company, and that's what they wanted to be working on even when they weren't officially at work.

Edit: I should make a distinction here between startups (organizations that are intended to grow really fast) and small businesses. I know several small business owners with good work/life balance: you kinda need it, since a small business is a long haul that'll consume you if you don't have some other sort of life. I don't know any startup founders with a life, during the startup phase.

Know what sort of business you want and be honest up-front with family, friends, investors, employees, and yourself. You aren't going to get rich in 4 years with a small business. But you can make a good living for yourself, sacrificing less of your personal life, with significantly less risk. If you're going to shoot for the moon, figure out what it would take to prove that you're aiming right, and bail out before you sacrifice too much if you're not.

I know a lot of startup founders. Most of them work hard, for sure, but also have some balance. Some more than others. The two aren't incompatible, but it takes some work to make them otherwise.

Not to mention that most of those Type A busybees' startups will fail. All the hours in the world can't erase the fact that even good startups often tank, and most startups are founded on pretty cockamamie ideas anyway.

Equating hours-per-week with value is naive at best.

"For every Mark Cuban there are 1,000 entrepreneurs who succeed without working 90 hours a week."

Is there are tangible evidence for this? I agree with the idea of diminishing returns, but also think that one needs to put in more than 40 hours a week. But so far, the arguments are anecdotal.

I certainly haven't done a study, no. I'd love to see one too.

I believe there has been some evidence that supports the ~40 hour work week. I suppose 40 exactly is a tad arbitrary, optimal number is probably some strange decimal, but I'd be surprised if it wasn't really close to 40 for the average person.

Perhaps it depends on the individual, perhaps for some its 40 and for some its 50, etc. Maybe the latter group succeeds more. I feel like this is untrue, but certainly can't prove it.

right on.