Ok guys, lets put some facts in.
Copy Paste from a study (Yan Chenghong)
The significance of reduced thrust takeoff.
Prolong the life-circle of an engine by reduction T3.
As we all know,the longer the engine life is,the higher profit and the lower operation cost is.Turbine,as main part of an engine,is easy to be damaged for its bad working condition with high heat load,great centrifugal force and anomalistic pneumatic force. The great centrifugal force will wiredraw the blade. The anomalistic pneumatic force causes vibration and affixation stress to blade,then blade is easy to fatigue and rupture. The turbine inlet gas temperature (T3*) is an important factor of turbine power.Increasing T3* leads to increasing blade load and decreasing metal intensity.It is showed that the metal life has logarithm relation to its temperature.
For example,a blade lose 35 percent of its life under the condition with 705 ℃ after operating 3,500 hours but 51 percent under the condition with 870℃ after operating 6.6 hours. The reduced T3* (about 30 to 50 ℃) when taking off with reduced thrust lengthens twice life of the heat section.
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Ok that was clear enough despite his english..
Laker Airways was the first airline using reduced thrust method in BAC-111's in RR Sprey engines. Rolce Royce had noticed that engines sent for overhaul by Laker airways were the best maintained of any BAC-111 operator.
Dont forget also, that lower takeoff thrust settings could permit a takeoff where with full thrust it wouldnt dispatched, with V1 limited by Vmcg, in short/wet runway. So you can increase your weight or if field limited reduce the ASDA simple by using reduced thrust.
Flex is, a great tool.