Will unused spare razor blades rust if stored for a long time?
Aside from storing a in dry location, you might use a vapor corrosion inhibitor (VCI) in a container with the blades. Amazon offers a similar product for ~US$11. 

My experience has been that VCI is effective and does not leave a noticeable film that needs to be removed. Whether this is cost-effective for your intended use is another question (perhaps you can use the remaining VCI on other objects or share with ten other people). 

And then, beards are even more cost-effective ;-)