I am retired from 45 years as a analytical chemical technician. The cellulose nitrate breaking down would form nitric acid but the cellulose acetate forms acetic acid hence the vinegar smell. In looking into the storage of the dice I believe it should be keep cool and dry, possibly using your refrigerator and packing nearby some backing soda to neutralize and vinegar that would be released. I would not pack large amounts of dice together as it is the vinegar gas that will affect the other dice. Remember it is the heat and humidity that starts the breakdown of the cellulose acetate.