Ask Steve Gamble in Newberry, FL. Do whatever he says.
Fyi, I'd never own another plastic zipper after the short lived I had on the four I received via warranty on my Bare. Also, I'd never again own a Bare, lol
I have had several people advise me to switch to a plastic zipper because they did so years ago and have had much better results than with metal.
I guess it just goes to show that not all metal or plastic zippers are created equal. Chances are, better and worse products exist in both categories.
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As for the original question, I think you should trust the manufacturer to know what is best for their product. The manufacturer is the one who did the research, development and testing. I don't believe the advice would be purposely bad (reducing product service life) because that would damage reputation & sales. As long as competitors exist with reasonably similar products, that would not be profitable.