How long should a workday be?

This might not be the right question, given that two people can produce very different impact in the same amount of time, doing exactly the same work under the same conditions. People who would self-describe as perfectionists can spend double the time on something that is perfectly useful in half the time. Without meaningful connections during work, people have to spend a fair amount of time making up for it on social media. Meetings and emails are mostly low-return time sucks.  There are better questions that address the value of time at work.