Remember, if you buy new, the chassis will be covered by the chassis manufacturer. For example, our Ford E450 chassis was warranted for 5 years or 60,000 miles. All of the appliances on board the RV carry their own warranties, usually about a year or so. So, what's left? Basically, the integrity of the box. Would buying a warranty for this part of the rig be worth the annual or semi-annual inspections? Only you can decide this.