The bottom line is this...

I have made three week long trips to Moab (along with numerous other trips) on stock birfields with the following modifications:

1st Year - 32 inch BFG Muds, Open Differentials, Stock gearing

2nd & 3rd Years - 33 inch BFG Muds, Detroit rear, Truetrac front, 4.88 R&P & 4.70 T-case.

I have done the majority of the difficult (not the "extreme" ones) trails in Moab including Pritchett Canyon and several difficult ones in Colorado (in the 1st year build) and did not break anything.  I have replaced a couple of universal joints since I purchased the truck.

The key to not breaking them is don't use the throttle while turning and  minimize the bouncing.  When I climbed Rocker Knocker Hill I broke all the rules.  I started on the far right side, locked the steering goinging left and bounced my way across the face of the ledges until it when up, nothing broke.

I recently installed 30-spline Longs because the thought of actually breaking them makes me    and I recently upgraded to an Aussie in the front.  Unless you have a locker, if you drive smoothly and reasonably you shouldn't break them often if at all.