So I don’t think batch brew loses its flavor over time, I just believe the flavor changes. Partly due to cooling and also compounds inside the coffee aging. We let our batches live for 75 min, if it stays full in the caraf. If we serve some out of a full container right after brewing we only let it live for another 45 min. We only brew half gallon batches that we dial in pretty heavily, then brew into a half gallon container so the thermal mass is as best as possible to keep everything as up to original temp as possible… hope this makes sense!