The 60:40 ratio allows the Nebbiolo to show its best characteristics (floral aromas, a bit of tar and roses really, and those amazingly energetic, fine-grained Nebbiolo tannins), while the Mourvèdre plays the important support role (mid-palate presence, approachability, and a bit of spice). In short - the Nebbiolo provides the flash, and the Mourvedre makes it drinkable in your lifetime.