Another 'no' to warranties. Put the money in a separate account and you'll see that you won't need it. Your RV is new and has a warranty. If appliances are going to break they'll do so in the first year.
We full-time and travel constantly. We bought our MH new in 2004. Everything is A-ok with it.
Tires for Alaska in two years? Again, we traveled to Alaska in 2009 the last time. Since our tires were from 2004 we chose to replace them all before the trip as they were getting due. We had no problems on the trip. The roads are no worse than some of the two-lane roads in the lower 48. Just drive slow through repair/construction areas.
Warranties are a waste of money.