Class C full timing downsides

The chassis used on class C's tend to be pretty reliable, and usually outlast the house part if cared for reasonably well. The E series chassis most commonly used for class C's is also used for many commercial vehicles like ambulances, shuttle busses, smallish box trucks, etc. and many of them (and the vans the chassis is derived from) last for at least a few hundred thousand miles. That's not to suggest that repairs or maintenance at a shop are never required, of course, and naturally that does involve your house going to the shop, and the workers there entering it and so forth. If the shop is reputable and the workers honest, that isn't a problem. Unfortunately, there are a few shops and workers that are less ethical than would be wanted...and many that are entirely upstanding.

I don't think anyone offers a lifetime extended warranty. On average, you'd be money ahead to not get the extended warranty, as the companies that offer them are charging more than they on average pay out (or they wouldn't be able to stay in business). Really they are more of a breakdown insurance policy than a true warranty.