I've had mixed results with zipper boots. The original ones on the truck held up for years. Once it got torn, I replaced with a Northstar? part. Boot failed in a couple months. It acted like the grease melted the boot. Contacted the seller and he shipped a different manufacturer's boot. No issues. It seems to me that the fundamental issue is the material type. I can't see how a non-zipper versus a zipper boot really makes any difference in regards to life expectancy.