have your local shop install Enduros bearing kit into your XTR cups, the bearings have larger balls and a much better seal to keep out the moisture. Our shop has bearing for about $15-20 and about the same to install.
I think you are referring to the plastic shim. It's the thin plastic piece that covers the dust seal and extends over the I.D. of the bearings. When/if you get the Enduro bearings you will no longer us that piece b/c the Enduro uses larger balls and has a smaller I.D. that actually fits on the spindle without the need for that spacer.Even after popping the first cap off I could see the bearings around the inside edge of the cup under the second "protective" seal.