octaneman

There is no exact science that will tell us how long the lifespan of an alternator or generator has. . Its job is to keep the battery fully charged and to provide a steady supply of electricity while the engine is running. A byproduct of producing electricity is heat, which is why every alternator has an integral fan to push cooling air through fre alternator, plus lots of cooling vents CM the front, back and sides to let the heat escape. To keep the alternator from overheating, make sure it's clean and free of any dirt, grease or other debris on its exterior. Anything that traps the heat inside the alternator will kill it in short order.
If the alternator is loose, it will be subjected to jarring and vibration, which may damage its internal components. Also, most alternators rely on their mounting hardware for a grounding source. So a loose alternator will not be able to deliver its full rated output to the rest of the electrical system, due to the voltage drop at the poor grounding point. The alternator will be forced to work extra hard all of the time, in what may be a losing battle to keep up. An overworked alternator will die an early death.