Idling is not a good idea. Especially at the lowest possible idle.
This has been discussed a lot and one thing I got from it is that if you are going to let a diesel idle for more than a couple of minutes you need to keik the RPM's up a little so the oil pressure will stay up.
On my B7510 it will idle down to around 1,000 RPM so it leave it at 1,200 to 1,300 if I amd going to let it idle for very long. That is the recommended RPM for warm up in the Kubota manual (could be wrong here, my memory gets worse every day).
I ran mine mostly in the 1,500 to 1,800 RPM range with some short spurts up to 2,000 for the first 50 hours and tried to vary the RPM's every 5 or 10 minutes.
Some folks say run them like you are going to use them. It turns out that now that I am slightly past 50 hours I still seem to run in the same range most of the time. It works well there.
Bill Tolle