Just a few notes regarding the ongoing discussion. There is no doubt in our mind that the best enclosure will not avoid chemical decay of acetate film.
Climate control is the key decision.
Cold storage is the only way to optimize acetate film stability. This applies to newly processed films and to already decaying films as well. I'm keeping a first series of degraded motion picture films some in sealed cans and other in vented cans inside a freezer, and a second series at room conditions. At the start of the experiment all films were at the autocatalytic point. Six years later, the acid content measured in the films kept at cold temperature didn't change.