Here in the Great Lakes they say that the standing rigging can last longer than 10 years, due to the lack of salt water. But, unless you can't afford it, why not just replace it every 10 years & sleep better? I have an unstayed 16' 8" mast, and you would not believe the stresses that can be observed starting at about 10 knots. If you're lucky, a busted mast will only scare you half to death, and not actually kill you.