[debergalis]

Engine manufacturers typically specify a TBO -- Time Before Overhaul, which is the number of hours in service an engine can run before it needs to be torn down, inspected, and overhauled according to the manufacturer's procedure.

For the most part, commercial operators must adhere to these recommended times, but aircraft operated under FAR Part 91 (roughly, those that aren't used for commercial transportation) aren't required to follow the TBO recommendation. You can run it as long as you want.

In practice, most operators do follow those guidelines. I've never heard of any engine doing much more than 2x the TBO before requiring major overhaul. And you'll often need various repairs to cylinders and engine accessories along the way.

Interestingly, manufacturers also specify calendar time limits on TBO, but private operators commonly ignore these. Lots of airplanes only fly 25 hours or so a year.