The dullness Im not sure I understand.
that being said, my wife did put one of my better knives away once, without thoroughly wiping it dry, and it did develop a spot of rust. This spot was not on the cutting edge, so it didn't affect the function.
But, I guess if the water does react with the metal on the cutting edge, it could affect the cutting function.
But then again, what do I know
Im just thinking out loud ( which could be dangerous)