This really depends on how cleats are used. We often see nylon cleats that are over 10 years old, when they have been used for light loads on control lines. However, tensioning a rope by dragging it back through the teeth will quickly burn out a nylon cleat. This is why alloy cleats were originally developed. Alloy cleats withstand this type of use, as long as the rope is clean. A dirty rope that is full of sand will wear out any fitting. Windsurfers and kitesurfers who have to rig on coral sand beaches certainly know that their equipment has a limited life. Hard anodised cleats have slightly better wear resistance than silver ones. Nylon cleats are completely resistant to salt water corrosion. They are also resistant to many acid and chemicals. Alloy cleats have "excellent” corrosion resistance. Hard anodised cleats have slightly better corrosion resistance than silver ones.