Advice for older Golden Retriever?

Hi,
I have a 9-year-old Golden Retriever. He has a beautiful, shiny coat,
no sign of white hair (which I see all the time in Goldens that are
younger than him). He is already having hip problems though, and has
problems getting up or going down stairs. I have given him Cosequin
for about a year and a half now, keeping the dosage low, but raising
it occasionally when his legs seem to be doing worse.

I have fed him Nutro dog food for about 2-3 years now.

I am just wondering what kind of improvements I can make on his diet?
Is it normal to be relying on Cosequin for the rest of his life? I
don't mind paying the money, but I just don't know whether there is a
better solution.

I know that my raw vegan diet may not apply very well to my Golden
Retriever. But at the same time, the same fundamental rules of food
combining, protein digestion, enzymes, etc... still apply to all other
living organisms. I'm not concerned about making my dog vegan, but I
am concerned with allowing his body to achieve the proper mediums for
digestion. I just can't help but think that packaged dog food has
horrible combinations of food that are vital, but should not be eaten
in the same meal (much less the same bite!).

I would love to hear how other people have to say about this subject.
Thanks so much, I really want to do the best for my dog, and I know he
is starting to get old.