I would suggest getting an oil analysis kit from some place like Blackstone Labs. Have the dealer fill the test bottle from the draining oil after about 1/2 has flowed out. Pay the $20-25 for the analysis once or twice per year. This will give you a baseline early in the truck's life and will tell you with some hard data if the extended interval is too long or not.
The test can give you early warning of other problems too - even things as simple as needing to change the air filter.
Independent of the oil analysis, I would go for a change before the trip. It seems like a hassle to to to arrange one in middle of a trip.
Also, is there a severe duty table in the owners manual? See if towing falls under severe duty and if the oil change interval is reduced.