Originally Posted by white lobster
To answer your original question, it's not a bad idea to carefully pop the seals off of an old cartridge and smoosh some new grease in there. If it's just dirty (and the races aren't pitted), clean grease can add a lot of life to the bearing. New cartridges tend to be cheap, but they can also be hard to find, since most shops can't stock every size.
Once the seals are off, cartridge bearings are fairly easy to clean out. Make sure you blast them with compressed air when you're done to make sure all of the solvent is gone before you put grease back in.
This guy knows what he is talking about.
I service cartridge bearings all the time, Chris Kings seals appear to be designed to be removable.In fact, the service interval for cartridge bearings is the same as for cup and cone bearings, 3,000 miles in dry conditions, 1,500 miles in wet conditions. I like to use White Lightning Clean Streak to degrease the bearings becuase it dries very quick and doesn't leave a residue. Just be careful that you don't distort the seal when removing them.