If you are reloading expressly for the purpose of long term storage here are some tips;
1. After final tumbling of the brass handle while wearing white cotton "conservator's" gloves. This will keep from depositing any oils to the cases and help prevent corrosion.
2. During the reloading process keep the air dehumidified.
3. Pack the finished ammunition in clean new paint cans as sold at Lowes.
4. Include a large desiccant pack inside each can.
5. Label the can with the contents and the date of packaging.
6. Store in a cool dry environment that has a minimum seasonal temperature range (a dehumidified basement).