Humidity kills metal...
Even here in AZ,.. the first Harley muff I put on went after 15k miles. I downshifted and shot the center baffle plate out the rear on an afterfire (saw it fly in my rearview mirror)... like a mini cannon...
We don't have the constant humidity of many places here, but the wide variance of temperatures between day and night causes condensation in tanks and mufflers.
Rust kills...