I guess the word "tune up" doesn't really fit, but just wondering if these are an item that should be periodically replaced even if they don't look like they have signs of wear? I haven't typically seen people say that every x number of years or miles they should be replaced, but I have seen some places online that say after 8 or 10 years they should be replaced as standard maintenance. It kind of makes sense, because rubber does get old after a while...I just bought an 04 Suburban, so that means the flex lines are 11 years old. I'm planning on replacing all my hard lines with the Dorman stainless kit, so I was thinking while I'm there maybe I should just replace them all, what do you all think?

(It kind of also begs the question; even if you buy new ones who's to say they haven't been sitting on the shelf somewhere for ten years...)

 

You may want to replace them for the same reason you are replacing the hard lines. If that reason is rust then their likely rusted together anyway.

 

I guess that's a good point