How often you rotate will ultimately really depend on your dog. Both of mine have sensitive stomachs so frequent rotation is not really an option for us. I feed a mix of kibble and wet and usually keep my kibble constant (I feed Innova EVO kibble). I do not rotate their kibble any more frequently than every 6 months, but usually I don't even rotate it that often. I do however rotate the wet/canned food they get more frequently because it makes up a smaller portion of their food intake. I buy a large variety of different premium brands (Blue Buffalo, Natural Balance, Cupboard Creations, etc) and formulas of canned food and rotate the canned formulas every 4-6 days.