I renegotiated my job down to 4 days taking a 20% salary cut (a bit less because of progressive taxes). I’m a bit flexible, sometimes working 5 days a week and then 3. This is a win-win for me and my employer because in dire times I can sometimes work 125%.
On the downside it feels I do about the same amount of work as I was doing when I worked 100%. Just less slack. But then I’m well paid for my 80% (after some raises).
I had a similar situation and also felt like I was getting the short end of the stick sometimes; I was working harder during those 4 days than I was when I was working 5 days. But 3-day weekends every week are so amazing. It's like taking a 20% paycut to change an hour-long commute into a 10-minute commute (which, 2x/day and 5x/week, would be the equivalent time advantage). which is also definitely worth it.
I find it odd people are willing to take such a huge pay cut. A lot are probably working more hours each day, and in any case could have negotiated 4 days with zero pay cut. There is a case to be made that the week wouldn't be 20% less productive, and not quitting for a job with your preferred schedule is a win for the employer...
On the downside it feels I do about the same amount of work as I was doing when I worked 100%. Just less slack. But then I’m well paid for my 80% (after some raises).