I can't imagine why in the world anyone would put in time and effort to take apart a bearing and not re-pack it with the best grease available. I've worked in a lot of bike shops over the years and when I started using Shimano Dura Ace grease on hubs I noticed that the grease on the outermost surface was dirty, but the grease under the "cap" of crud was clean, it didn't migrate like white lithium grease. I was working in a friend's shop about 10 years ago and I was doing a little work on my own bike. I was overhauling the rear hub on my touring bike with an XT rear hub (M 750). There was only some cheap grease that looked like Noxema face cream on the bench (like many of you, he wasn't too picky about grease). The little voice in my head said don't use it, and I would't have if I was at home, but I was in a rush and packed it with the thin white stuff. A couple of years go by and I really didn't ride in the rain over that time, just a little wet pavement, a lot of commuting and an occasional dirt ride, never in the mud. The hub was never out of adjustment over this time. Imagine my shock when I opened up the hub and noticed the first signs of pitting on the cone. I point the filthy finger of blame at the cheap grease.
And the lower headset bearing gets a ton of wheel spray on any bike without a fender. One long ride off road on an old style loose ball headset and it's like you packed it with Comet scouring powder. Grease liberally. I can't count how many bottom brackets I've taken apart and been greeted with a few mL of rusty water. But of course, bicycles don't spin at high r.p.m. or have ICE temps and loads on them, so people think grease doesn't matter. I suppose in a way, grease doesn't matter, but CONTAMINATION DOES MATTER.