Agree with CP,
, I store all my down hanging up, jackets, sleeping bags, are hung up in either wardrobe or 'built in' wardrobe, depending on length.
Things like sleep mats, Exped Down, Synth. and TMR are stored 'flat' with valves open.
Only put into stuff sacs shortly before I'll use them. If not going to be used for a while, (a week or so), will take out of stuff sacs and 'store' as before.
Paul