Can't really help you there, but I was told that alu cups and case with stock gears should last a while, even under hard BL conditions. Proper shiming is also a good idea.
Those UE diffs are a bit overpriced, IMHO.
Welcome to the forum, btw.
There's just a simillar discusion going on:
http://www.rc-monster.com/forum/show...=&threadid=702