Frosting doesn't just give your cake a creamy layer of flavor -- it helps retain its quality. Cakes lose their moisture and dry out over time, but a layer of frosting helps seal that moisture in, and your cake tastes like it's fresh days after you make it. If you frost it too soon after pulling it out of the oven, though, the cake will fall apart, so don't rush into it.
How Long to Wait
When you pull your cake out of the oven, it needs to cool completely before you can frost it. To expedite that process, remove it from the cake pan -- you can make this easier by lining the cake pan with parchment paper before you bake the cake. Allow the cake to cool on a wire rack. Frosting a warm cake will make it crumble and fall apart, so wait until the outside is completely cool to the touch before you start frosting it. You can also make the frosting process easier by using room-temperature frosting, instead of frosting that has been refrigerated. This makes it creamier and easier to spread, so it won't pull at the surface of the cake and create tears.