Generally, there are enough preservatives in dry dog food to keep it on a shelf for near a couple of years, if it's stored in a cool, dry place, and well sealed.

I try to keep a few 40lbs bags on hand along with a couple of special 25lbs capasity totes that I feed my sweet, picky lil' monsters from.

You might want to be careful what other storage aids you use in the dog food. Many dog foods have a certain degree of moisture and/or oils that make it somewhat palitable to the animal. Some storage aids can leach out chemicals that won't mix well with these.
It's best to just store animal foods in a well sealed container and store in cool, dry places out of any sunlight.

As mentioned by Harbinger, rotate on a regular basis.

A dogs digestive tract, for the most part, is very strong. Dogs and many other animals can bury a dead carcass for as much as two weeks, come back and still eat on it with little to no ill effects,(or followed by eating grasses to aid digestion or calm a sour stomache from it. but then, many animals eat the bones and all too. the calcium in the bones helps calm their stomaches).

I've seen coyotes in the wild survive on a diet that seriously would make a billy goat puke,(nasty, smelly, pest-ridden, dirt-filled, and half rotten... whatever it was). Oh btw, I have a great receipe for "Coyote Stew"... who wants to come to dinner? I've heard that, "Dog makes a fine meal..."

Michael