There have been several owners who are in the 170,000 + miles on their trucks. They have acculated them very quickly using their trucks for daily work trucks. Mostly towing. These folks have reported a few problems, One had a blown engine, Probably the worse report. Others of cooling leaks, and other repairs. For the most part it looks like 200,000 is a doable goal.
Of course you will have to evaluate if those that put 170,000 mile in in 2 years are working their trucks easier or harder than your daily type of driving. Theirs are definitely more hiway miles. Albeit under loads towing.
My truck is currently at 67,000 miles and other than maintenance has been almost trouble free. ( front stabilizer bar and tranny selenoids at 36,000 miles) Other than that it hasn't seen the dealer. My 6.0L's usually started having more serious repairs that required a stay at the dealer around 100,000 miles. So I'm watching to see what becomes a common repair on these engines as they approach that milestone.