I am currently looking to get an insert and have narrowed it down to the Jotul C550. I have an installer recommending a steel stove rather than cast iron. He said that the cast iron stoves are put together with tongue and grove panels and over time the cement will not last (that is the reason you only get a 5 yr. warranty) and a lot of the steel stoves have lifetime warranties. Is this true? and will I need to replace or repair the stove in 5 to 10 years? Thanks