Sorry to contradict your father, but unless you're putting your plane on a hard (very hard) metal surface you are not going to damage a blade. A metal blade resting on a wooden workbench is not going to notice it. In fact I would venture to say resting them on their side is more dangerous as they may encounter each other in that orientation. But if you choose to follow your father's advice instead of mine, I totally understand and encourage such loyalty. Just be careful what you bump into those exposed blades with, including knuckles.