Well that is good that he is healthy. At that age it might be worth have your vet run a blood panel to see if there is anything hiddin that would show up, like a liver problem, etc.

Feeding a high quality kibble is good but feeding a raw diet is better. Even just supplementing with raw is a benefit to a dog's health.

I used to feed my old dog a raw chicken thigh, bone in, in the morning and a half scoop of good kibble at night and she did excellent on that diet for years. I did add the oils too and she had a few table scraps at times.

Here is a useful site about grading dog foods --

http://www.reviews.com/dog-food/

It gives a good run down on the foods with more meat in them and made by companies that had not had a lot of recalls.

I have been feeding Earthborn and Fromm to my new pup and both are high quality kibbles. I also feed her some of the Blue Ridge Beef raw Puppy Mix which is an excellent raw food.

So you might consider added some raw meats to his diet and trying a better quality kibble, and adding the salmon oil and coconut oil, both of which are very helpful to an older dog.