Long-term seed storage

[reliquary]

I'm accumulating seed to store in what my wife is calling a "Doomsday Box."  I already store the ones I use, from one year to the next, in the crisper of the refrigerator. 
 
I'm looking at storing them for several years, in case of TSHTF situations.  Some have said they store theirs in the freezer without any significant problems. 
 
Does anyone here have any preferred methods, and how long will seeds normally last in cold storage?

[keith44]

From what I see, moisture content and a constant (cool ) temprature are the most critical to seed storage.  With a low enough temp you could easliy store seeds for a couple years.  Seeds stored at a constant 60 degrees in low humidity have remained viable for three years for me (corn, cucumber, squash).  I would reccomend rotating seed stock regularly, and saving only heirloom, and open pollinating varieties.