1. A method of increasing information content for content-based image retrieval (CBIR) systems, comprising the steps of: providing a CBIR database, said database comprising an index for a plurality of stored digital images using a plurality of feature vectors, said feature vectors corresponding to distinct descriptive characteristics of said images, said characteristics comprising defects of said images, anomalies of said images, or both; calculating a visual similarity parameter value based on a degree of visual similarity between features vectors of an incoming image being considered for entry into said database and feature vectors associated with a most similar of said stored images; determining whether to store said feature vectors associated with said incoming image in said database based on said visual similarity parameter value; when said incoming image and said feature vectors associated with said incoming image are stored in said database, determining for at least one among said incoming image and one or more associated feature vectors a storage lifetime based on said visual similarity parameter value, the storage lifetime indicating when the at least one among said incoming image and one or more associated feature vectors is deleted from said database; and maintaining said CBIR database by deleting stored digital images from said CBIR database based on said storage lifetime associated with said stored digital image, wherein if said visual similarity parameter value of said incoming image is less than or equal to a first threshold value, assigning a short-term value to said storage lifetime associated with said incoming image; wherein if said visual similarity parameter value of said incoming image is greater than or equal to a second threshold value, assigning a long-term value to said storage lifetime associated with said incoming image; and wherein if said visual similarity parameter value of said incoming image is between said first threshold value and said second threshold value, assigning an intermediate-term value to said storage lifetime associated with said incoming image, wherein said second threshold value is greater than said first threshold value.