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It's worth noting that BMW added a plastic liner (#11 in red) to the upper half of the rod bearings in the next generation (B58) of this engine. The documentation states that this was necessary due to the increased number of starts these engines are expected to see with the auto start/stop feature (though many N55's also use this feature). I suspect the real story is that they wanted to move to 0W-20 (LL14) oil for fuel savings and saw from the N55 failures that the bearings were already going dry even with the old 5W-30 oil.
Hey fatso, one thing that would be pretty interesting to us all "in the name of science" would be to plastigauge your old bearings first. If you find a clearance out of spec it would suggest that the bearings wear with age, presumably to the point of excess/failure. But if there is no measurable wear it might suggest that the issue is due to oiling problems such as debris from an OFHG replacement.
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