I've run a diesel farm tractor for over 20 years for mowing and snow removal and have discovered that many times success is all in the battery. I had a problem once when I tried using summer blend in the winter (duh) but other times my tractor might fail to start if it had not been started recently (not a fully charged battery). My tractor and my diesel truck both have told me that strong batteries really really helps, more so then in a gasser where compressions are lower and oils might not be as thick.
I have also discovered that weaker batteries in the 2005 F350 truck can cause the FICM control module to fail (in the winter or summer).
My recommendation is to keep your batteries fresh and keep the connections clean.
Edited: I'm glad to hear that the 6.7 is performing well for you Brooks379. 6.0 owners tend to look ahead in that way.