Well, people usually recommend you rotate brands as they are less likely to become allergic if they have more variety... but the fact is that dogs can still have adverse reactions to switching around in good dog foods. I know quite a few dogs had to get off Natural Balance just because of a TINY little switch around in the ingredients.

And also, every dog is different. I know Honda didn't even need any transition time. That dog could eat anything and be fine. >.> And she did have quite a few times where she ate stuff she shouldn't have... and well, the wrappers came out in her firm poop. Lol We called it her christmas poo. hahahaha These adverse reactions could have just been because they didn't have a 'transition' time and so they had diarrhea or something... I'm not really sure. But once you change the food with your dogs enough times, I think they become use to the transitions and don't need a transition time anymore.

And even if the ingredients do change... just make sure they are good changes and not bad... and maybe do a transition time with the last bag if your dogs aren't used to changing so they don't get upset tummies.