BINGO to vranasaurus !
The manual cleary states if the OLM has not suggested so, to change the oil after one year.
I would suspect that your driving pattern is very much highway and not city. We are almost done with 08, so it also seems as if you are not putting too many miles on your truck.
I took the time on my 05 Honday Odyssey to guage it's OLM ... I was using MC, so a blend and the OLM was accurate. I myself choose to simply stick to a 5k interval.
Your use of M1 and following the OLM would be a great choice. Simply following a 5-7k interval would be a great choice as well given the use of full syn.