In the early days Bristow in Oz used Wessex on a particular offshore contract where it was SOP to shut one down in the cruise. Reportedly I believe to have dropped fuel consumption by 25%, which was the aim as they were operating at their extremes of range. Regulator required flight above a certain altitude so you had room to get the other one started (hopefully) should the operating engine fail. Wonder what the innocent pax would have thought, had they known. Still, different days back then.