Repeatedly over the years, I've interviewed supervisory folks sporting long experience in commercial janitorial service. Most often, they cite multiple jobs, usually titled "operations manager" (general or regional), some for smaller owner-operators, most from the various cleaning franchises. 
In virtually all cases, they report "operations" involves both day (interacting with customers) and night (training, supervising, filling-in) work, ongoing. They also cite long shifts, multiple responsibilities, and much pressure and friction from higher up.
On founding my business, I had the privilege of working both day and night. Didn't like it, so as soon as I could, I put a supervisor on to run the night operations. I called him our "operations manager". Didn't expect him to work days - at all. As best I can recall, in the close to 40 years since I stopped working both days and nights myself, I've never asked anyone to do so. I found that doing so causes irritability (in turn causing friction with others), hurts concentration and decision making, leads to (usually "dumb") mistakes, and impacts health. Sounds like what my competition features in their business models.
Caught a review in the Journal several weeks ago of "Why We Sleep", by Matthew Walker. He discusses the effects of sleep deprivation, such as irritability, concentration and decision making, and mistakes. Curiously similar to what I notice working both days and nights. Not a good way to run a business.
At more of a societal level, Walker delves into research on mistakes attributable to sleep deprivation in such fields as health care (think residents working 30 hours. Not 30 hours per week, but a straight 30 hour shift. And no more than two of those per week, interspaced by a couple of 12 hour shifts.) Also, he mentions the indications of sleep deprivation leading to the Chernobyl melt-down, and the Exxon Valdez oil spill.
By Chance, I recently read "Sea of Thunder", Evan Thomas's narrative of WWII in the Pacific. The book focuses on the battle off Samar, during the Leyte landings. We see lots of mistakes - in communication, judgment, intelligence analysis, friction causing lack of communication among folks who needed to communicate: most notably among Halsey and his staff, also at Pearl and in the forces covering the landings, and also among the Japanese. Illness, and exhaustion stemming from over-work and little sleep, affected all of those folks. And lots of servicemen died.
Didn't get quite enough shut-eye last night. I'm posting this and then going home to bed.