I'll chime in, as was mentioned earlier Deere extended all of their intervals out to 500 hrs. with the advent of their own CJ-4 lube along with USLD. Other manufacturers engine design/usage had played a large part in what their own OEM intervals were.
Since Deere makes no on-road diesel engines, their intended use was in either ag equipment or heavy equipment, both of which are "dirty environments" and require more frequent maintainence vs. on-road equipment, which for the most part is a much cleaner environment for an engine to operate in, which is why DD, Cummins, and others have had extended drain intervals for years in OTR engines.
I have a very good friend who is, at least for my area, a very large farmer. We have the same Deere engines in very different applications, with mine being in marine service, which is probably the "cleanest" environment an engine can operate in. He is marveled at the amount of engine hours I get out of my equipment vs. what he gets before overhauls. We not only use the same engine oil, but also the same fuel supplier.
The main difference is whether its in a combine or earth moving equipment there is always dust, a lot of dust, not only coating the outside of the engine, radiator, and everything else, its also being ingested.
The Deere Plus 50 II line is very good for its intended application, along with all the others mentioned in this thread. As many of us have proven over the years some engines do MUCH better with different oil. Deere's intended purpose for the Plus 50 line is worst case scenario dirty environment use. OTR engines are probably the easiest on oil, with somewhat constant RPM.
