1. A computerized method for determining a model refresh rate for a model representing a list of network user identifiers, the method comprising: receiving, at a processing circuit, a first model representing the list of network user identifiers at a first time and a second model representing the list of network user identifiers at a second time, wherein the first time is prior to the second time; calculating, by the processing circuit, a level of similarity between the first model and the second model; comparing, by the processing circuit, the level of similarity to a threshold value; and determining, by the processing circuit, the model refresh rate for the list of network user identifiers based in part on a comparison between the level of similarity and the threshold value, wherein if the level of similarity is less than the threshold value, the model refresh rate is a predetermined rate.