Fabrics need air to breathe, that's why the stench when you opened up the space bag and the zip lock bag. All you really need is acid free, not archival. If you have doubts about an organic surface, get an acid testing pen. They're cheap, readily available, and easy to use. Mark the surface and read the color, a real no brainer.
Go with the easiest, cheapest, safest storage method that works efficiently for you and don't worry about it. Life's way to short to worry about this particular "what if". I guarantee you, whomever you give your finished quilts to isn't going to think about archival storage one little bit and you wouldn't want them to. You want them used, not archived, right?