A method for sampling images includes receiving a first image set generated by automated imaging equipment during a first inspection period, and storing in a memory an image library that initially consists of the first image set. A plurality of new image sets is then sequentially received (302) during respective inspection periods. While the new image sets are received (302), the image library stored in the memory is updated. Updating the image library includes, for each new image set, adding to the image library a certain number of images distributed among the new image set and removing from the image library the same number of images distributed among a current instance of the image library (308). The number of overwritten images in the image library decreases from one inspection period to the next.