There are studies out there showing that productivity is proportional to days spent on the problem, not hours. It's likely that for a knowledge worker, sustained schedules with long workdays actually reduce average productivity.
It makes logical sense-- combine the ability to work long hours (rare) with talent and you will blow the normal fatigue-able people out of the water in terms of output and (in a sorta-meritocracy) rise to the top.
I know an entrepreneur that bought a well known franchise. He told me he worked without a day off for the first year before finally taking a Sunday off. My gut was to call bullshit. Employees around from that time confirm. He's very successful today.
It's been awhile since I've read it, but I remember reading something along those lines in "Drive: The Surprising Truth About What Motivates Us" (http://www.amazon.com/Drive-Surprising-Truth-About-Motivates...). The thesis is that our motivation to do things is along a spectrum of intrinsic (for the love of the work) vs extrinsic (e.g. money). Generally the former yields better results. Some studies even showed that paying people to do things they love can be detrimental, because you're now adding an extrinsic motivator to something that they are intrinsically motivated to do, thereby making what they love feel like "work."
In spanish, "empirico" means exactly the same thing. Based on well tested observations, not your just "personal experience". Sure it is a little overused some times, but it still means some degree of confidence greater that "in my experience"
Citation needed.
There are studies out there showing that productivity is proportional to days spent on the problem, not hours. It's likely that for a knowledge worker, sustained schedules with long workdays actually reduce average productivity.
http://www.jamesshore.com/Articles/Business/Software%20Profi...
There may be some exceptional people who can defy this rule, and it's possible they are concentrated in startups, but I'm dubious.