Like Karlin said above there, I switch my dog's food 4-5 times per year. I do stay within brand though. I feed Timberwolf Organics. They have a nice variety of flavors and my dogs do very well on them. I don't have a distributor near me, so I order direct from them online. Shipping is included in the cost of the food, and service is very good.
I mix in a bit of Merrick canned food with each meal (2x p/day). They have wonderful flavor varieties that are a lot like stews that people eat.
~not knowing how near the truth is,
we seek it far away~