With problem solving jobs, like software engineering, you end up with equal or greater productivity. There is a low-level of constant burnout that occurs with

With problem solving jobs, like software engineering, you end up with equal or greater productivity. There is a low-level of constant burnout that occurs with 5 day weeks, but you don't notice the difference between feeling normal and that low-level burnout until the first week back from holiday (after which it starts again). I've simulated 4-day-weeks before using annual leave one day a week spread out over a prolonged period, and those times have been some of my most productive. Every week has had that post-holiday high.