So had very recently first hand experience, my diff has only just been refitted ready for the Fish and Chip run. A couple of things to note, my 2 year old, only 2000 mile (2 track days) diff had NO significant wear. In fact the only wear was the new plate high spots had been taken off, there was no need for any service work to be carried out on the clutches. The reason for my diff removal was to solve a reoccurring noise/vibration problem which had been present from new. This was eventually traced to a bad UJ, so hence the diff was already removed. One recommended is not to separate your wheel bearings from the driveshafts, if you do you will almost certainly end up replacing both. If you are assembled new driveshafts and wheel bearings try using bearing anti fretting paste, but even then there is no guarantee fretting won't occur.