That was the better part of a year in my life, continuous. Of constantly considering that every decision, every meal, every movement, every action at all times, and weighing it against the risk of impacting my ability to respond to a customer call. Maintaining an extended period of alertness for a threat that very rarely materializes is frustrating in many ways that I'd like very much to forget.
I didn't burn out from it, but it was a major factor in my decision to resign from that company. Obviously people out there that can handle this lifestyle, but I couldn't. And frankly I'm quite content to never try again.