SandBlaster-214,
This often comes up, and is worth a bit of explanation.
In a few words, if you push the engine at 5 minute power for 4.5 minutes, then reset to something lower, then go back to the 5 minute rating, so that you are operating nearly continuously at 5 minute power, you will be seriously damaging that engine. Your overhauls will occur much more frequently, and perhaps failures occur much more often.
That the pilots would believe that the engine "cools down" so that it can be abused again is indication that they do not understand how aircraft components are rated.
Imagine that the engine has 10,000 beans in a jar when it is built, and that these beans are withdrawn at the rate of 1 bean per hour while it is at 75% cruise power. If you cruise at 60% power, the beans might be spent at 1/2 bean per hour. At 30 minute power, the beans will be expended at 5 beans per hour. At 5 minutes take-off power, they will be consumed at 20 beans per hour. At OEI power they will be consumed at 100 beans per hour. Once the beans are gone, the engine has warped blades, shroud rubs and poor power. Its vibrations are high, and it is closer to failure. You can spend the beans as you wish, but clearly it costs you more to use the engine above its rating. These ratios are not too far off from the real ones, I think.
The engine gains no benefit from cooling down between the cycles, because the time at the cycles is doing damage, as every running minute does damage. It was George Saunders who once wrote that metal has a memory like an elephant, and it will recall everything to did to it. We call it creep, where the blades are being bent, warped and grown as they operate at elevated temperatures.
When the manufacturer rates the engine, he tests it against a assumed spectrum, which accounts for the power vs time it will operate. The spectrum is a guess on how the engine will be used, and a way to predict overhaul time.
The trick your pilots are using is unwise, and unfair to the owner of the helicopter, and also in technical violation of the limits. The 5 minute rating is a take-off rating, of course.
Does this mean that a guy who takes off every 5 minutes and uses Take Off power to do so is wrong? Nope, because he is taking off! His engines will be more harshly used, but he is legal. He would also be wise to come off of take-off power as soon as possible each time.
Remember the beans in the jar.
Nick (absolutely NOT Al Einstein!) Lappos