Stallboy:
Wouldn't the main problem with all these engines be that they are reaching the end of their life. You can only rebuild any piece of machinery so many times before it becomes unreliable even with the highest standards in the workshop. The stresses that are put on all the components of a gas turbine are truely incredible.
No that is not the problem at all. These engines are the proverbial grandfathers axe.
The critical components are repaired and/or replaced regularly. Stuff wears out and gets replaced all the time.