Do you have any good brands that have different formulas or meat sources? My main food has four different meat sources, but I also switch to a different formula, same brand from time to time. The base ingredients are similar so it's not so hard on the dog's system. When I do this I haven't found the need to slowly switch, but most of the ingredients are the same or similar enough, just the meat change and mine are fine on all the different meats.
If you can't do that I would stay on the same food for longer than 3 months. It sometimes takes 10 to 12 weeks to really see how a dog is doing on a food. I would give a food at least 6 months if the dog isn't having any issues with it. If you decide to do a rotation diet you need to find compatible foods to rotate with. You can't go from a lower quality food, to a higher quality food, to a low quality food, then to a high meat based food.
I usually revisit my food choice every 6 months to a year, but have stayed with my current brand for several years now.
