When to Overhaul
The smart way to deal with engine maintenance—including deciding when to overhaul—is to do it “on-condition” rather than on a fixed timetable. This means that we use all available condition monitoring tools to monitor the engine’s health, and let the engine itself tell us when maintenance is required. This is how the airlines and military have been doing it for decades.
Source: When to Overhaul – Savvyaviation