Because the moon lacks an atmosphere, there is no wind or water to erode or wash away the Apollo astronauts' imprint. That implies their footprints, roverprints, spacecraft prints, and waste stuff will be maintained for a very long period on the moon. They will not, however, remain there indefinitely. The moon is still a changing environment. It is regularly pummelling with "micrometeorites," which indicates that erosion is still occurring on the moon, although slowly.