Thanks so much for all of the feedback, it is so very helpful.
It seems that so far there has not been a failure of the DPF reported due specifically to the type of driving I expect to do. There were problems with the early 6.7's, but as noted they were continuing to tweek the computer routines in those early years. At least it does not sound as though the DPF is going to unexpectedly fail in Whoknowswhere, Nebraska leaving me stranded with 12,000 pounds behind me. But that obviously does not mean it couldn't happen or that some sensor or other part won't strand me anyway.
So I don't know if this is the best or worst scenario.
Before I was thinking I would be limiting to a 5.9, but now I am feeling more comfortable with a 6.7. The 5.9 is much more simple and the trucks with them are much cheaper. Cheaper, older, less comfortable, less tech to go wrong, but none the less older..... The 6.7's are much more money, more tech, but newer and much more cushy from what I read. I like the styles of the 2010's+. But being blessed (or cursed) with the ability to turn a wrench I am automatically drawn to cheaper/older stuff. (Blessed "because I can fix it", Cursed because everything I own is old..., "because I can fix it"...) And yes, I know I am
Thanks again for the real life experiences. Some day I will have to make a decision. Please keep your experiences coming!