The answer to this question is very complex. As Broke stated, all turbine engines have life limited parts which are generally disks, hubs, and sometimes shafts. The manufacturers try to design the engine so that the published lifes for these parts within an engine are generally about the same so the operators don't have to pull an engine because one part has a life limit of say 5,000 hours while the remaining parts, which might have limits of 8,000 hours, still have 3,000 hours of life, which are referred to as stub times. Airlines generally do not like to install stub time parts as it means they have to pull their engine back out of service ahead of schedule. The design life limits are really driven by where an engine is used. Turbine engines that are used in Part 91 operations generally have published life limits that are in the 6 to 8,000 hour range. Turbine engines that are used in Part 121 operations typically have published lives around 30,000 hours, or more if the part is cycle limited and used on an engine that is typically on long haul airplanes. The difference between the Part 91 and 121 operators is how fast the airlines run up the time on their airplanes. Many airlines will fly their airplanes between 2,000 and 3,000 hours each year and they would be up in arms with the manufacturers (more than they already are) if they had to scrap out their very expensive rotating parts every 2 or 3 years. The published life limits do not mean that an engine goes into service and remains on week until it reaches the life limits of its parts. Some operators remove engines at prescribed intervals for inspection and overhaul, or for unscheduled repairs due to FOD, birdstrike, or internal failure or damage. When an operator pulls an engine varies from operator to operator based on the reliability history of an engine in general and also at that operator, and the maintenance schedule of the airplane. (An example would be if an operator did a C-check at 12,000 hours, they would try to coincide the engine removals with that check rather than have to bring the airplane back into the hangar to do an engine change.) Other operators monitor the engines' performance and remove an engine once it has deteriorated to a certain point in what is known as on condition maintenance (OCM). Most airlines are using a combination of both OCM to monitor the engine for any premature deterioration and will pull it to prevent a failure but also have a soft time limit on when they will pull an engine for inspection or overhaul. It is not uncommon for operators to fly 10,000 to 15,000 hours between scheduled removals. Some operators such as those based in Hawaii will not build up that many hours because they fly such short routes that their removal schedule is based instead on cycles and they may get 5,000 to 8,000 cycles out of their engines between scheduled removals. Occasionally, and I mean occasionally, some engines just go and go and go. There was a European operator that ran a pair of JT8D-15A engines on a 727 out to the 30,000 hour life limit. They had removed the third engine at around 25,000 hours just to see what it looked like and decided to keep the others in service so long as they maintained good EGT and RPM margins. There was a CF6-80C2 on a 767 operated by a US carrier that was in service for 30,000 hours before it had to be removed for a scheduled insepction. And there is an RB211-535 that is on a European operated 757 that the last time I heard had something like 36,000+ hours and was still going strong. Engines designed in the West (Europe and North America) have much greater reliability and service lives than engines designed elsewhere. When the CIS was certifying the JT8D and JT9D engines for use in that country, their airworthiness officials requested information on the typical lives of these engines. After seeing how high the numbers were, the requested and were provided with documentation to confirm those numbers. They then stated that the average overhaul life of a Soviet-built engine on an Aeroflot jetliner was less than a 1,000 hours!