I store mine in a plastic baggie inside a black plastic film canister. It keeps them out of the elements and away from UV degradation.
Major contributors to oring aging include air, contamination, light, and ozone. Eliminate these and you maximize your oring strorage life.
Most buna orings are rated for 15 years of storage at optimum condition. Poyurethane are only rated for about 5 years of storage at optimum conditions. However, it has been studied and documented that many of these types of orings last well beyond these dates if stored properly. The starting conditions of the orings might not be quite as good as they were when brand new, but they quite often still meet the necessary criteria for installation as a new oring. So, don't throw out your old orings just yet.
Except for the Automag in front, its usually the man behind the equipment that counts.