The Microlon film will last until removed. Microlon penetrates the pore structure of the metal and becomes an integral part of the metal. In a properly treated engine all wear happens at Microlon-to-Microlon surfaces instead of metal-to-metal surfaces, reducing friction. The micro-thin film can only be removed by machining it out or by heating the metal to 775 degrees Fahrenheit. If the film is damaged by anything that makes it past the air filter, the Microlon film has a self-healing property that will repair and thin spots or scuffs. There are millions of engines that are performing as well today as when they were first treated.