In order to model a better quality Earth without distortion at the poles, I decided to use a cube, subdivide it 3 times and then to-sphere it. It works much better than a UV Sphere and than an Ico Sphere for the same reasons. All the faces are squares of similar size and if you use a cube projection, you will have no distortions and best texture quality.
As the material properties of the ocean and the continent are different, I used a Principled BSDF shader for each one and mixed using a texture of the ocean mask.
My problem is that as I need 6 images, one for each side of the cube, I duplicated the same material and just changed the texture. But if I work on the shader of the ocean, only one side is affected. I want that all sides share the same ocean and continent shaders since only the texture is side dependent.
How can I do it? Thank you in advance for any hint.