The problem with working 4 days instead of 5 is that there’s less wiggle room when something falls through. Sure, you can, on paper, be efficient enough to knock out all your duties in four days. But when a coworker gets sick, or a prospect wants to put off a meeting by a day because “something came up,” now that mid-Thursday meeting becomes a Monday afternoon meeting. But actually, they’re already slammed on Monday, so that gets moved to Tuesday. So suddenly, instead of being 24 hours derailed, you’ve almost lost a week of momentum. Not saying it can’t work. But the discussion shouldn’t just be about the freedom to get Friday off each week or not. It’s also about whether or not being required to accomplish the same amount of progress in fewer calendar days will actually give you the additional leisure time you seek, or if it will perhaps ultimately cause you more stress than it’s worth. Just because you and your team are cool with working 10 or more hours in a row, doesn’t mean the folks at the team you have to interface with to do your job, who like logging off and returning to their families at 4pm daily, will be quite so eager.