Dry milk products are highly sensitive to environmental conditions, particularly temperature and moisture. Their vitamins A and D are also photosensitive and break down rapidly if exposed to light. The area where your dry milk is stored should be kept as cool as possible. Air-conditioning or even refrigeration can greatly extend the nutrient shelf life. If the storage container is transparent or translucent then it should be put into a second container opaque to light or stored in a dark room.
Dry milk will absorb moisture and odors from the air so storage containers should be impervious to both air and moisture. The drier it can be kept, the better it will keep which makes the use of desiccants is an excellent idea. Oxygen also speeds decomposition so vacuum sealing or oxygen absorbers will decrease the available oxygen. Because of its fine powdery texture gas flushing with nitrogen or carbon dioxide generally yields poor results. If the dry milk you purchased was not packaged for long term storage then it should be repackaged right away.
Clean, sound plastic one and two liter soda bottles can also be used, but probably should be used just once since the plastic is somewhat permeable and will hold odors. If you have access to a can sealer, #10 cans make wonderful storage containers for dry milk, particularly if used in conjunction with O2 absorbers.