Crevice corrosion in standing rigging that "looks" ok can cause catastrophic failures without any apparent reason. Riggers sell a chemical wash that can be applied to standing rigging. When used properly, it is supposed to ''flag'' crevices and other abnormalities in the metal so you know they are damaged and can replace them before they surprise you. The rule of thumb is to replace the standing rigging a week before it fails. For some people, this means every 10 years, for others, this means they don''t replace it. Sailing is a balancing act between risk and enjoyment, all the time.