This might be a strange question but how long do blades stay sharp while in storage? I ordered a sample pack of 100 blades (order hasn't been packaged or shipped yet) and I figure each blade will last about a week so I have about 2 years worth of blades. Do the blades loose their sharpness over time without use and still wrapped up? I'm thinking oxidation and erosion of the edge. I'd hate to do a bulk order once I find the blade I like only to have to throw a bunch of them away because they became dull with age. Thanks.