The 12-14 days is crucial here, I think: The US Army tested battle readiness and effectiveness off and on since WWII and found that you can keep a unit working

The 12-14 days is crucial here, I think: The US Army tested battle readiness and effectiveness off and on since WWII and found that you can keep a unit working well for a couple of weeks with about 4.5 hours a night. After that, they start to have serious problems. Less than 4.5 hours a night and the problems start a lot sooner.