My son is 8 weeks old, and we started using this at 6 weeks. He would only take 30 - 45 minute naps during the day, but now that he uses this sleep sack, he sleeps for 2 - 3 hours! His stretch at night has extended to 1 - 2.5 hours, which is huge when he was only sleeping for 3.5 hours at a time. We have an Owlet and his sleep quality has also improved; his sleep score is always great, when it was either poor or okay before. We love this so much that we already have the other sizes for when he g...