A guess based on a Google search suggests a rail lifespan anywhere between 5-99 years. Lightly used industrial spurs could easily have rails that are 90 years old or more, whereas a curved piece of track with high frequency, fast, heavy trains might only last 3-4 years. In terms of maintenance, rail grinding is used to keep to track smooth, and maintenance teams inspect the track periodically (obviously not enough in North America). If I recall correctly in Japan the Shinkansen tracks get inspected every night for safety and upkeep, a great way of keeping high-speed trains safe and fast.
A guess based on a Google search suggests a rail lifespan anywhere between 5-99 years. Lightly used industrial spurs could easily have rails that are 90 years old or more, whereas a curved piece of track with high frequency, fast, heavy trains might only last 3-4 years. In terms of maintenance, rail grinding is used to keep to track smooth, and maintenance teams inspect the track periodically (obviously not enough in North America). If I recall correctly in Japan the Shinkansen tracks get inspected every night for safety and upkeep, a great way of keeping high-speed trains safe and fast.