I agree with deandec on this aspect. A new coach, of good quality purchased from a reputable dealer and manufacturer, will nevertheless have teething issues for a year or so. These will likely be covered in toto by the new vehicle warranties. In years 2-5 you're probably still relatively safe from catastrophic failure. Beyond that, it starts to get like casino blackjack-- its all about the probabilities.
In my case, I bought a 10 y/o coach full of OEM appliances and systems. When I sat and thought about this, it seemed reasonable that one or more of these would fail between the age of 10 and 14. So, I covered my bet. Its just that simple.
The "put the money in the bank" proponents will come out ahead if they have no big failures, or failures they can repair themselves on the cheap, but they leave themselves uncovered in one important area-- the drive train. Frankly, I'm not very worried about that, because these engines and transmissions are designed (with proper care) as million-mile devices. However, this is a place where a low probability event has to be covered, because even one occurrence can be a total showstopper.
That's all it is-- you want to keep RVing,, so you cover yourself against the things that could prevent you from doing that.
John, Diane, and Lincoln, the guard cat. RVM103
Fulltimers since June 2012
2002 Dutch Star 40, Freightliner, Cat 3126, 2004 Element