Hi Bob,
My unit is a class C.
I've done 75,000 miles. Here is a list of failures:
Bad connection to the water pump--inconvenient, but not a trip ender. It meant using the campground facilities, and carrying some bottled water for drinking and cooking.
Bad board in the air conditioner/heat strip--taken care of under warranty by the seller.
Mass air flow sensor. Ford advised to continue the trip unless the V-10 started to run rough.
Blown fuse for alternator charging of the OEM house battery bank. Replaced and upgraded with an automatic circuit breaker.
Crack in windshield. It does not interfere with sight lines so I'm still using it as is.
As part of normal wear and tear I've replaced the brakes.
I did replace the brake master cylinder--but probably I was being over cautious.
I have upgraded to larger wheels and new wider/taller tires.
I purchased the unit which is a 2004 used in 2009.
There have been many instances of screws needing to be tightened--but I see those as normal.
I put away 20 cents per mile for maintenance. I'm definitely ahead of the cost curve so far.