I bought a set of 20 year-old NOS Shimano Deore XT hubs on eBay. They clearly are box-new, never used, but the rear hub seems to have a somewhat gritty feel to the bearings, plus the freehub turns with a bit of effort. And the front hub is either adjusted too tight or there's something else preventing super-easy turning of the axle, and there's also a little bit of gritty feeling.
Is there something I should know about grease/lube sitting for 20 years? I don't have a 17 mm cone wrench yet, so I haven't opened them up (also waiting for a response from the seller). Is there any reason to expect corrosion from sitting around? These were in the box, and don't look like they went through a flood or anything.
If the seller is alright with it, then I will disassemble, de-lube and re-lube them; otherwise they go back.