They can be overhauled/reconditioned indefinitely however nearly all the highly stressed rotating parts (disks, fan blades, main shafts, etc) have a cyclic life limit since catastrophic failure of these is not tolerated. Upon reaching this limit they must be removed from service. These life limits are hard regulatory limits. Other limits can be varied by operators based on their experience.eg. a Middle Eastern operator might find it necessary to perform tasks more frequently or have a reduced on-wing life because of the high temperatures they operate in and sand/dust ingestion whereas a temperate climate operator may be able to extend the intervals and on-wing life.