What would Jack do?

As an experiment in human limits, great. As a sustainable and effective way of running your business, absolutely terrible. Keep in mind the following (assuming you are a normal human being and do not have special powers, like Jack Dorsey): 1. The human mind can only maintain sustained focus at the highest levels for a limited amount of time each day, which is why in a typical work day, performance drops significantly after 3PM.

2. When tired or exhausted, your mind will default to system 1 thinking (using Nobel winner Kahneman's description for fast, intuitive, emotional and automatic decision-making process because it requires less energy; from his book Thinking Fast, and Slow) which is normally bad for start-ups that require intense focus and deep insight.

Accept that the human mind works very well in matters requiring problem solving skills and creative deliberation for 4-5 hours, the other 4-5 hours leave for less intense duties (responding to routine email, basic accounting, staff meetings, exercise, playing with the kids, etc.). To push your mental focus so hard will render you a complete zombie by nighttime and your significant other will leave you, make no doubt about it, because it would be like talking to a wall that just nods and blinks. I know, been there, done that, both as the zombie and on the receiving end of a zombie.

Simply put, 16 hour work days will destroy your family and wreck havoc on your creative process. Although it may be great for those engaged in routine debugging that is almost automated and rythmic, I simply don't see this approach to work as useful for anybody in a position requiring problem solving or creative focus.

I like the idea of thematic days.

Some days i just feel like writing all day. I should do all the writing for everything I am working on.

I could also setup meetings for all projects on certain days.

Finally, like my dad say, it is all about discipline. Without it, it is not going to work.