It will not ever get brand new engines.
Every disk from the compressor section to the turbine section has either a hourly life or as Cycle life or both. When this is reached the engine has to be replaced as most disks cannot be changed on wing. Sometimes the first and second stage compressor disks can be done on wing.
The only other things that will make them remove an engine and send it for over haul is a new AD
issused, FOD damage, or performance problems. Turbofans are very consistant machines. You can trend engine performance based on N1, N2
, Fuel flow and EGT (my job now). If these parameters change you can see it. It can be an indicator of damage or problems.
Engines in the airline fleets are pretty much on condition meaning as long as they are not broken they do not come off.
Two years as stated above is not normal for engines lives. Even our JT8D-XX's last much longer than that. We tend to go 8000 Cycles / 16000 hours between changes. They usually are pulled for FOD or performance problems.
Also note thrust reverse has NO bearing on engine life. Also engine times only count flight times. You can ground run an engine for 16 hours and it will add no cycles or hours to the engine times. However some huskits will drop the life of the Turbine disks on the JT8D-XX depending on the P/N of the disk installed.
Sometimes all you can do is look them in the eye and ask " how much did your mom drink when she was pregnant with you?"