I have always been apprehensive of extending OC's on either of my 6.0's due to all of the oil side injector failures I have read about. The guys on the 6.0 forums change at 3,000-5,000 mi.
I am sure, at least the way all of my UOA's have come back, that I could do 10,000mi OCI's without issue. Maybe the next OC I'll do an TBN test also to see where I'm at.
I'll slow down the second half of December and then see if I can get something put together using notepad or something similar to "notebook" my UOA's.
This grade/brand of oil seems to work fine in my application, at currently 166,xxx mi. this truck has been absolutely the best vehicle I have ever owned, with my wifes '06 Milan a very close second.