My GSD's were all put on adult at 6 months of age.This was recomended by my breeder of 22 years.And having them switch to the adult did no harm what so ever.Tron is 8 and was a working dog(retired Police Dog.He retired cause he had a touch of arthritis.Yukon(R.I.P)was also 8.You just need to make sure it's a premium brand of food.Wllness,Innova,Chicken Soup for the Pet Lovers Soul...No Iams,Dog Chow,Science Diet or any of the other crappry foods.Just make sure the first 5 ingredients do NOT contain corn.When introducing the adult food,make sure you mix a bit of the new with the old for a while till.My sisters 3 huskies and border collie where put on adult at 6 months.Two are 8 and 2 are 7.All in perfect health.All on premium food.Hope this helps.