We use data from the TREC routing experiments to explore how relevance feedback can be applied incrementally - using a few judged documents each time - to achieve results that are as good as if the feedback occurred in one pass. We show that relatively few judgments are needed to get high-quality results. We also demonstrate methods that reduce the amount of information archived from past judged documents without adversely affecting effectiveness. A novel simulation shows that such techniques are useful for handling long�standing queries with drifting notions of relevance.