For a few years at least... I once found a piece of fishing line that had been immersed in water for quite a while, and it had become brittle and fragile... I wonder if chlorine in the water had something to do with it.I've been wondering for a few days...what about a piece of mono-filament fishing line? That should jam the threads just a little and, if you believe the environmentalists, it will last for 10,000 years.