Yeap, credit rating is a major factor in insurance rates. But that wasn't GN2ZDGS question.
From what I've seen, extended warranty rates tend to jump after about 5 years. Some companies don't want to write policies after about 10 years, but Good Sam, for example, does up to 16 (I think). We didn't buy another polict after our 7 year plan expired - it did not look like a good financial bet to us.
Insurance should actually decline with age, as the value goes down. Liability rates stay the same (or go up with inflation), but collision and comp fall off some. However, you probably cannot get replacement value insurance after about 5 years.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL