Items insulated with lofty material such as down or synthetic loose fill and synthetic batting should always be stored uncompressed for long term storage. Never packed into a stuff sack or underneath other items for long periods of time. I like to hang them up. Obviously jackets, sweaters, vests, etc can all go on normal closet hangers, but I recommend the same for my sleep systems. I specifically do not sew hang tabs into my sleep systems because of the catastrophic tear out potential. Instead, hang them on a hanger from the top opening where there is the elastic drawcord. If someone were to pull on it, instead of tearing some critical seam out from a hang tab, the drawcord will simply stretch off the hanger. No big deal. If no hangers are available and/or you want to hang on a hook I recommend doing this by the top drawcord as well. Just by the cord itself, where it exits the drawcord tube. You can just loop this over a hook. No, it won't be able to slip off, but at least the elastic of the cord will stretch and take up any load placed on the bag/quilt.
Obviously, when we are out on the trail, the reason we bring these types of insulation is their ability to compress and fit in our pack and so compressing them is a necessity. However, the loft we use to keep us warm is created by the fibers acting like little spring, holding up the loft. If a spring is left compressed, it looses some of it's ability to do this. Different materials react differently to this. Synthetics typically will suffer the effects of compression much more than down, which is very resilient to compression. However, it too is like a bunch of little springs that inevitably will react to compression cycles and long term compression. You'll hear tales of "I leave my down bags smooshed in compression sacks for years. Pull them out and they're fine!". Well, they may seem fine, but it's likely due to the overstuff making up for some loft loss. Maybe it'll be noticeable, maybe not...but you can be sure that every compression is some level of a dent in it's ability to loft. So, it really makes the most sense to only compress your insulated items as small as you need, for as long as you need. If you have room in your pack, no need to smash your sleeping bag into a tiny compression sack. Let it fill the space and give your pack structure too. When you set up camp, take these items out and give them a nice shake and fluff. Let them loft up before you need to crawl in for warmth.
Obviously, when we are out on the trail, the reason we bring these types of insulation is their ability to compress and fit in our pack and so compressing them is a necessity. However, the loft we use to keep us warm is created by the fibers acting like little spring, holding up the loft. If a spring is left compressed, it looses some of it's ability to do this. Different materials react differently to this. Synthetics typically will suffer the effects of compression much more than down, which is very resilient to compression. However, it too is like a bunch of little springs that inevitably will react to compression cycles and long term compression. You'll hear tales of "I leave my down bags smooshed in compression sacks for years. Pull them out and they're fine!". Well, they may seem fine, but it's likely due to the overstuff making up for some loft loss. Maybe it'll be noticeable, maybe not...but you can be sure that every compression is some level of a dent in it's ability to loft. So, it really makes the most sense to only compress your insulated items as small as you need, for as long as you need. If you have room in your pack, no need to smash your sleeping bag into a tiny compression sack. Let it fill the space and give your pack structure too. When you set up camp, take these items out and give them a nice shake and fluff. Let them loft up before you need to crawl in for warmth.