with the Amazon stuff, how long it lasts depends on your environment. If your bilge is dry, and you dont keep the boat on the water, it will last longer than if you run wet, and store it at the lake. This goes for factory parts as well, BUT the mean time before failure on the factory part is likely going to be years longer than the aftermarket parts. One other thing to consider is that aftermarket part may not really be "marinized"... they will say it is, BUT since its a "cheap" knockoff, do you really trust it deep down in your bilge where the fumes collect..... Should something go sideways, is that company going to stand behind their product? Moral of the story, buy once, and cry once.... get the good quality parts and be done with it. Even on a 3.0 that starter isnt so much fun you want to keep doing it......