I have studied metallurgy and the science is that the metal razors are made from is generally heat treated. This means that once set, the micro-structure of the metal will only change if heat (significantly high) is applied. Unless you leave your razor to rest in an oven, I can see no reason that the edge of a razor would change. The longer the razor is left to rest, the greater the corrosion to the metal and therefore cause dulling of the edge. This is why a majority of straight users oil their razors, because the oil helps prevent/ reduce corrosion of metal. Not forgetting of course that the environment you leave your razor in will affect the corrosion, humid environments cause more corrosion - this is why I don't leave my razor in my bathroom.
I hope this helps :)