I've been selling Penn State pepper grinders very successfully since they first came out with them. Certainly well over 500 of them over the years. Long time back I made a few Crush Grind salt grinders to match (somewhat), back when they had a metal screw holding everything together. About 4 years after someone started using one, they complained that the screw had corroded and fallen out, so I stopped making them. Penn State now has a 'salt grinder' that matches their pepper ones and I jumped on it, buying a 25 lot, before finding out that there's a little metal spring inside it that will be exposed to salt. Has anyone found out how long these things last in actual use?