I have heard of rotating foods, one of the people that own a pup I bred does this often. She feeds, Eagle Holstic, California Natural, Innova, & Wellness. She switches about every 6 months or so.
Whenever you are switching your dogs food, it's good to gradually do it over 3-4 days so you don't upset their tummies. And I wouldn't switch puppies under 6-7 months old often.