Reduced operating temperatures will increase engine turbine life without negative engine performance or structural impact on other areas.
The reasons for the increased turbine wear could be poor turbine blade material properties, excessive turbine tip gap clearances or more likely excessive tip gap clearances in the compressor.
The tip gap clearances are often associated with bending and/or ovalization of the engine case structure (Thermals, manuevers etc.)
There are plenty of performance curves available to the tech side of your house to show you what you will get if your crank back on the throttle and EGT at cruise