True 24/7 can be really disruptive. I've had consulting gigs where some people would rather call me at 3AM then talk with the person next to them in the Ops room. Irritating as all can be, having a sleep schedule disrupted. Same customer ended up having you come in for a normal work day, cater supper, have you do evening deployments/change control/bug fix, then the late night/early AM stuff on prod would start till 5/6AM. You could possibly grab a couple hours of sleep before starting the 'normal' next day - but it was easier to just pound through a 32 hour day and then collapse on the airplane home. Nothing productive happened from those long days. Just like water skiing, more and more mistakes happen the longer a person is at it.