Yes airlines too. Shutting down an engine in cruise was standard operating procedure with Aeroflot in the early 90's - at least that was my experience as a SLF back then. Personally I see nothing wrong with it.
AdamFrisch is correct with his reference that endurance (not range) is independent from altitude. These curves are normally not published in AFMs unless you operate a military patrol aircraft. When you look at these curves, best endurance is surprisingly flat between some low altitude like 10000ft right up to tropopause.