[greendesk]

I feel that there were times when working 24 hours / day was effective and times when working such long hours was ineffective.

There are two issues that I know of when I worked for long hours: tunnel-vision, communication and burning out.

If one works long hours, one has to evaluate an idea all the way, to check if is correct or not. For me, his hampers evaluating competing ideas effectively. This might not be the case for everyone.

Working as a team requires feedback from other team members. If you get stuck or need feedback/communication with someone else, you can enter a feedback loop such that the additional time that you spent on it does not bring additional value. These type of loops are possible even if working less hours per day, so it can be a good idea for additional research.

And burning-out: there is only so many hours in a day. A worker can have interest outside the technical question at hand: if they have priorities outside of work, would you require that they forego their priorities for work?