P3s routinely shut down one or more engines to extend endurance generally because they were also operating at a relatively low altitude, say 15,000' and below. They also shut them down for range when forced to remain at low altitude. For example, patrol work was routinely carried out at say 9,000' and below and you were there for eight hours or more. Shutting one down in those circumstances saved a lot of gas. The jets I later operated only had one engine so options were limited in this area.
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