Hi Andyjoo and welcome aboard. Congrats on your new edition. It's not that these breeds shouldn't eat chicken or potato but there IS a high incidence of allergies to chicken with the breeds which typically display as skin type issues. Blue buffalo is a good food so if there's no issues with it you don't HAVE to change it. Any of the 'flavors' of BB Wilderness are going to have all the stuff that he needs as a high quality food. The fish based protein foods are typically better tolerated when dealing with allergy issues. I feed Taste of the Wild and have switched between the salmon based protein and the bison based protein with no issues and my pups are both just over a year old. But, again, if your boy has no issues then you don't have to change the food.
If you do change, you can technically change at any point - there is no right or wrong 'time' to change; just make sure you do it slowly to prevent the infamous 'canon butt'.
"Judging me doesn’t define who I am, it defines who you are"
"If you treat your dog like a human, they’ll treat you like a dog."