As an egg ages, the white becomes thinner, the yolk becomes flatter and the yolk membrane becomes weaker, making it more likely to break. These changes don’t affect the egg nutritionally or functionally but the freshness of an egg does affect its appearance. For attractive poached or fried eggs, the fresher they are, the better they will hold a compact oval shape with a thick white and a high centered yolk, rather than spread out in the pan. On the other hand, if you hard-boil eggs that are at least a week old, you’ll find them easier to peel than very fresh eggs.