If your dog needs them, then why not? The right answer merely depends on the foods and what your dog needs.
Basically, if a mixture of different foods better fits your dog’s nutritional requirements than any one single food, it can be an extremely beneficial way to keep your dog happy and healthy. Which at the end of the day is what matters.
Before you do, however, I would simply say this: always ensure that doing this is right for your dog and that you have the right blend of foods.