According to the appraiser/conservator I consulted for value and storage of several vintage quilts (my great-grandmother's), wrapping them in a white sheet and storing them in a plastic bin is the preferred method. Toss in a couple dessicants to take care of any moisture as well (the kind that come in electronics boxes are good). You can always crack the lid a bit if you're worried about it, but most of the time they let in enough air without having to do that. It's certainly safe for the six months you're talking about.