Labor laws prevent medical residents from working more than 80 hours per 7 day week, and, I believe have also capped the length of time they are "on" at 36 hours before they need to go home and rest for at least 8 or 12 hours.
EMTs and other healthcare workers are every bit as important as medical residents when it comes to preventing fatigue.
Tired people=people that make mistakes and harm patients. "Back in the old days we did it this way" is no excuse to make you do it this way now, especially when we know the harm that being tired can cause.