I use a trash compactor bag in the bottom of my pack - sleeping bag, dry bivy, and sleeping clothes go in there. That way they stay dry and not compressed. I had a bag a long time ago, and I sqeezed the crap out of it in a compression stuff sack. It never seemed to hurt it. I always stored it in the big bag it came with. That bag lasted 15 years before the fabric began to give out.