I am going to add my 2 cents to this debate. If you look at why the 4.2 diesel just keeps on going, it is because of the filtration systems on it. I have seen on the hardbody, the airfilter is flimsy, oil filter is very small, and diesel filter the same, thus leaving the engine open to easy factors of abuse. Is this lack of filtration not partially to blame? So, for me, I would definitely invest in upgrading the filtration system, particulate filter inline with the current diesel filter, and maybe an added snorkel with cyclone filter on top. Then, change the oil and filters every ten thousand km. I have one of these particulate filters on my Isuzu, and one cannot believe how much rubbish passes through the standard factory filter. This would directly mess up the injectors.
Also, one has to remember that the GU is BIG, and, although the 3.L makes adequate power, it is not made to travel all day at excessive speeds, rather keep a slower speed at lower RPM and keep those egt's at bay.
I have not heard of many blow outs on the 3L diesel after 2006, and would definitely look at the CRD when its time to replace the wife's Benz.
Just one more note, I have just rebuild a 80 series landcruiser 4.2diesel, with only 139 000km on it.....oh, and I am the third person rebuilding the motor. It happens to all manufacturers.