Hi barit1,
Your statement that the first few % is -
by far - the most significant effect on engine life is not supported by analysis from GE and SNECMA. Further reduction will significantly decreases maintenance costs, and improves reliability. You can find a good article on this topic by SNECMA and GE which was presented at the Boeing Flight Ops Conference in October. “ Reduced Thrust Takeoff— Proven Benefit, Lowering Engine Maintenance Cost”. You can find it on myboeingfleet.