Knot Longevity

[Billy V]

I always notice rust around the knot after using a rig.

This is abrasive and I would think it would compromise the knot. Even if I rinse it with fresh water it will still rust, so I do not reuse the rig.
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For unused rigs this does not apply, but it is reasonable to assume that a kink in the line is its weak point and a hook that is just sitting with a tied knot is a kink.