In several concept attainment systems, ranging from recommendation systems to information filtering, a sliding window of learning instances has been used in the learning process to allow the learner to follow concepts that change over time. However, no analytic study has been performed on the relation between the size of the sliding window and the performance of a learning system. In this work, we present such an analytic model that describes the effect of the sliding window size on the prediction performance of a learning system based on iterative feedback. Using a signal-to-noise approach to model the learning ability of the underlying machine learning algorithms, we can provide good estimates of the average performance of a modeling system independently of the supervised machine learning algorithm employed. We experimentally validate the effectiveness of the proposed methodology with detailed experiments using synthetic and real datasets, and a variety of learning algorithms, including Support Vector Machines, Naive Bayes, Nearest Neighbor and Decision Trees. The results validate the analysis and indicate very good estimation performance in different settings.