In 14 years we've had two show stoppers, both with our first coach, a poorly built Damon and both failures were engine failures resulting in a tow and some waiting (less than a week each). Tow covered by Coach-net and repair covered by warrantee.
There have been plenty of other failures, minor and nasty, that have caused us a day or two of waiting to fix. One slideout motor failed and we got the slide closed and drove on to a dealer that was next to the campground we had planned on staying at - so no time lost. Another nasty was a microwave failure so we stayed an played an extra couple of days waiting for the part.
I cannot remember any other failures that cost any time in the 14 years. Of course stuff comes apart from shake rattle and roll but a screwdriver and a wrench usually resolve those matters in minutes not hours.