Calculating a Compressed Memory State

A system's memory component compresses the four most recent key-value pairs into a single summary pair by independently averaging their respective vectors. What is the most significant trade-off inherent in this compression technique?

A system uses a moving average-based cache that summarizes the four most recent key-value pairs into a single summary pair. The current summary is calculated from pairs at time steps t-4, t-3, t-2, and t-1. When a new key-value pair arrives at time step t, how is the cache updated?