I have a 2017 Forester MBS 2401WS built on a 2016 Sprinter chassis with 32,000 miles. I bought a 5 year warranty from an online broker for about $2,550. I have viewed the warranty as for the coach and not the chassis. Thus far I needed one repair during the first year FR guarantee for a battery charging problem. I might have used the warranty for some other problems I have had but felt it was better to fix them myself or at least pay for the repair than to bother submitting a claim. The fact that I live in the country and am 100 miles away from the closest RV repair or dealer plays a part here though.
Mercedes has been great In taking care of problems with the chassis by towing the motorhome hundreds of miles when there was a problem at their expense. I've been towed from home to Denver ,235 miles, because 2 150 amp fuses blew and I couldn't start the engine and on a trip from Texas it went into limp home mode and I needed a 4+ hour tow to to fix a problem with the clean air exhaust system. I have used Mercedes for oil changes and scheduled maintence however, because I think it can eliminate any finger pointing when I have a problem. I do not feel confident with this vehicle since I have experienced a check engine light on 4 occasions. My daily driver, a Honda CRV, has been trouble free for the 82,000 miles and 5 years of ownership.