You should consider the possibility that you are wrong.
As I understand it, Henry Ford chose a 40-hour work week because he found that it maximized the total output of his employees. Computer programming is (minute-for-minute) considerably more demanding than working an assembly line. Maybe an average programmer maximizes her total output when she works substantially less than 40 hours a week. In fact I'd be surprised if that weren't the case.
And of course you could still run the service if you guys worked four-day weeks. Just make sure somebody's working on any given day.
Have you ever worked on an assembly line (or in a factory of any kind)? It's hard, backbreaking work that from my experience sucks much, much harder than any programming job I've ever had.
Hacking code may be more mentally taxing, but if you need to take break (for the bathroom or whatever) you can do it on your own schedule -- not on your lunch break like a lot of factory workers.
As I understand it, Henry Ford chose a 40-hour work week because he found that it maximized the total output of his employees. Computer programming is (minute-for-minute) considerably more demanding than working an assembly line. Maybe an average programmer maximizes her total output when she works substantially less than 40 hours a week. In fact I'd be surprised if that weren't the case.
And of course you could still run the service if you guys worked four-day weeks. Just make sure somebody's working on any given day.