batteries have a service life due to internal chemical changes from repeated use. Heavy usage shortens that.
Often the "500 cycles" is reduced to a 100 cycles because of heavy usage. Physical damage like drops to a hard floor can kill a battery.
Chargers DO NOT HAVE A "CYCLE LIFE".
Low quality/reliability may be a result of production errors such as poor soldering but a well constructed charger will last until killed by the user.
Power surges can kill a charger from the input end. Shorts caused by a bad battery can overload a charger.
Most charger failures are caused be heavy handed handling

The electronics in a charger could work for 10 years if not killed from the outside. Batteries have limited life, even if not used.