This depends upon the design of your valve, its usage case, its environment, media and how many times it is cycled. For instance if it is on a clean media, in a clean environment and not cycled regularly the life will be decades. If it is on a corrosive media and in a dry application with a high cycle rate the life will be much shorter. On our 90 degree turn ball valves we conduct regular lab testing and 30,000 cycles is a reasonable life cycle depending upon the application.