G'day Ian, I have two diesel Territories. One is my work car, the other for my wife/family. Each does around 50,000 km per year of country running, so a very different use to what you are planning, and I've now had 6 Territories. All except one has been excellent. The dud caused no end of trouble with fuel injection and gear box problems. Thank goodness it was still under warranty.
To cut to the chase, all modern diesels are very high tech and very costly to repair when they fail. If you're planning on keeping the car for the best part of two decades, expect an injector/fuel pump repair at some stage, and a bill heading towards an aircraft engine repair.