This argument can be applied equally against the weekend so I'm not sure it holds that much water. We've figured out how to have people work 5 out of 7 days, wh

This argument can be applied equally against the weekend so I'm not sure it holds that much water. We've figured out how to have people work 5 out of 7 days, what drastically changes if it becomes 4? What if it had always been 4? But to answer your question about coverage, $dayjob handles that with an on-call rotation and moving shifts for customer support.