I really appreciate my extended warranty. I have maintained different extended warranties for over 30 years, I can't say that they have paid for themselves, but they have paid some pretty hefty repair bills, allowing me to balance my budget over the years without an OMG experience. As for the CD idea, my current CD offers considerably less than 1%. Not a real good way to invest. Anything earning more would not be a fluid investment and might create a problem if I was hit by a big repair bill. I just had to change the cooling unit in my Norcold, $1,500, I paid $50. I also have life insurance, now you want to talk about a bad investment...there is absolutely no way to win on that one.
I think you made a good choice by getting an extended warranty. Just remember, FOLLOW ALL THE RULES...YOU MUST GET AUTHORIZATION FOR EVERYTHING. That said, the rules are really easy to follow.
Happy Trails.