Fernando,
Yes the certification is also a consideration.
But all turbine engines have life limited parts (LLP's) usually discs and blades but some engines have other items.
The LLP has a finite life, no overhaul,no rework just throw it away.
Engines with variable ratings have different lives for the same part number part dependant on the rating.
The higher the rating the lower the life.
As many of these part are in the middle of the engine, particularly turbine parts so that replacing a LLP can be quite expensive in work scope, apart from the cost of the part itself