It can vastly increase the life on an engine, by monitoring for trends in the engine, such as an increase of fuel flow, or vibration.
This infomation is downloaded after each flight, and any exceedances highlighted to the engineers. They can then take corrective action, such as carrying out a clean and lube to bring the vibration back into limits.
Alterations to the variable inlet guide vanes can improve fuel consumption and bring the engine back to it's most efficient.
It helped save Rolls Royce in the seventies with the RB211, as they could produce a more powerfull, longer lasting, more efficient engine.