I also follow two companies here in Sicily that I built in the past, one has six programmers.
So all the above is my "data source", that is not statistically significant.
I don't really think a programmer working 8 hours is going to be less successful of one working 12 hours per day: it is either good enough to be outstanding with the 8 hours, or will fail even with the 12 hours, since the productivity gained by experience, skills, understanding of the problem is the kind of 10x or 100x gain, while from 8 to 12 hours the difference is little (and, again, not sustainable for long time IMHO).
Startups are built by programmers, so I think the same applies to them as well, mostly.
In other words I could say that the output of a programmer correlates more strongly with the work it did to learn writing code, than the work it does writing actual code.
Another important thing is that having fun is not lost time if you want to build a startup. Recently startups are a lot more about providing an "experience" to the user, and enriching yourself in your free time can be very useful to provide something that people want.
For me it's an age thing. I put in some extremely long hours in my youth, and I think it paid off. I'm not putting in as many hours these days, but then again I feel like I'm quite a bit more productive with my time than I used to be.
I think it's the experience itself that's the differentiator, and not the fewer hours. In fact it's the experience that enables me to work fewer hours. When I was younger I really had to bang away trying many more approaches to solve a problem, and that meant longer hours.
However my father is like your father in this regard: he thought me to work long hours, and he still does even if it is 63 now. But I've the feeling that the work it does that has more to do with people, with moving from one place to the other to fix problems, and things like that, is much more "long hours compatible". The solve fact it does not sit all the day is different... In short I think that programming is exceptionally bad: too static, too focused, too stressing, too timelines, ...