I just finished making this beer last week. (6 days ago) I saw no activity in the air lock AT ALL, so I was reluctant to submit a review until I had taken another gravity reading. The second reading verified the yeast had done its job. This was a pretty big beer so there should have been 2+ days of activity in the air lock. There was none. In fact, the last beer I made using this S-04, had the same results. Acceptable attenuation, no activity in the airlock. Very happy with the results, though why no carbon dioxide? I removed the airlock on day three and heard some air leaving, so I had a good seal. Is this the new normal?