I'll post my same 2 cents I did on the other board. As long as you drive the car so the oil gets good and hot on a regular basis, yes the oil itself is good for the recommended 13K mile intervals. But it's what the oil is holding, which in the case of a diesel includes suspended soot particles, that worries me. And while the engine is close to bullet proof the same oil is lubricating the turbos with somewhat delicate bearings. For a $50K+ car, that I plan on keeping a long time (purchased, not leased), I sleep just a little better doing the mid cycle oil changes.
For duramax - once the oil change time limit expired for me, it stopped showing oil mileage completely and went as a red, change your oil alert.