I just went through this process myself and decided against extending coverage. My biggest fear is a major problem with the structure, for example, delamination. 'Walls, floors, roof, bumpers, glass, ' etc. are not covered by the two policies I looked at.
Numbers approximate: Good Sam had 50k? Mile / 7 Year plans that were about $300 per year with $1000 deductible (per year) and >$600 per year with $500 deductible. Most failures of systems (heater, fridge, AC, etc.) will be less than $1000. How many will happen per year? Also, Chassis/Drive train covered by Ford. Didn't seem worth it to me. The NICE thing about the GS policy is that you could cancel it at any time without $$ penalty.
Mind you I'm not very happy with the 20+ warrantable items I've had with my coach in one year but after getting them fixed, not much usually goes wrong in the 2-7 year time period except for the really expensive exclusions.
2015 FR3 30DS
2010 Ford Escape Toad