Interesting thread that I must have missed back in December so here are my thoughts.

As a sailboat owner who is working toward selling everything that doesn't fit on the boat and leaving for good it seems like I'm dealing with the issue of long term storage in a highly corrosive environment on a daily basis.

It's been my experience that unless whatever you are trying to "preserve" is completely clean and dry before you apply whatever preservative you are using there is the chance that there will be just enough contaminant present to cause trouble...and that includes treating a dry material in a humid environment. It could be those razors that seemed to dull while in storage were not as clean as you thought when you oiled them or at some point became contaminated due to a less than complete application of oil...and I'm not trying to slam you with this remark as I've had stuff rust that I had thought was bulletproof because some of the preservative had wicked off due to inadvertent contact with an absorbent material.

It's also been my experience with razors that it's pretty easy to damage the edge while prepping them or cleaning them for use after storage. Even tissue paper (or a Q-Tip) can dull the edge if you're not careful. The other thing I've noticed is when switching between different razors there is a short re-learning period before my technique is up to par and I'm fairly sure I've needlessly rehoned a few.

Or maybe you just have bathroom gremlins that sneak in a shave with your stored razors.