I use Costco lamb and rice. It works great and unless the dogs develop weight or other issues when older, I don't change it. Moose-dog turned 11 this past August and is in great shape. He's a newfie/shepherd/poodle so 11 is getting old for him - but other than a touch of back leg stiffness, he's got no issues.
Bat-dog is 7 and, as long as she doesn't manage to steal too much, her weight is nicely managed on the costco. She can tend to weight issues so I'll watch her as she ages, but she's done great on it so far.
When Moose-dog was young, he ate 4-1/2 cups per day. At about 7, I dropped it to 3-1/2 cups. When younger, his metabolism was extremely fast, now it's just fast.. He's maintained a nice 85lbs throughout.
Bat-dog has been on 2-1/2 cups per day and maintains a nice 65lbs.
Their coats are in great shape and no skin issues. And the lamb and rice has been good for Moose-dog's sensitive stomach.