[RACooper]

Well yes Mustard gas can remain viable for a long time (it's why French are still so careful cleaning up stuff from WWI), as well as other weapons.... however some (such as Sarin) or biological weapons have higher storage requirements to maintain the "optimal" viability of the weapon... for example a lot of nerve agents are finicky, if stored improperly they can become very unpredicatable.... I'm not saying that the weapons become safe after a set period of time... what I am saying is that they lose their military effectiveness after this time period becuase of the unpredicatablity of the results and quality of the chemical materials (ie. you gotta open the thing up to see if it's still effective) or that the storage/delivery vector is no longer viable (ie. the shells rusted through, or seals have been comprimised).

I suggest people that are interested should look up articles on the problems that the US Army Corp of Engineers is having storing/disposing some of the Cold War stockpiles in the south and mid-west. I'll see if I can find some links or some of my old material from NCBW training...