As John and Lucky says, as an AHJ I too am on 24/7 but luck has been with me. Not many emergencies since hurricane Sandy went by us. Then I was working every day. When I was in my own business, there wasn't a year go by when I didn't get an emergency call for a holiday. You name the day, and I know I worked it at least once in 15 years of my own business.
The worst part about that, was when I was in business and I went out on call, sometimes I didn't get paid by the customer. They needed me so bad on that holiday, but I couldn't get them to pay me for the service call.