I have known guys to not break-in things properly from gears to clutches etc..

I always went by manufactuer specs on all my stuff...especially on gears and clutches.

There is a right way and a wrong way to do things....not saying the "wrong way" means the rear will explode, heck it may last (I wouldnt know) but I do know these companies recc break-in's for the reasons Jeff has already pointed out.

Some of us don't want the hassle of short-cuts because people with my luck should understand why i try and take every precaution to ensure my car is done right. LOL