We have been using the Connectin tabs for our Chesapeake Bay Retrievers for quite a few years, after my sister told me about it.  (She has long used the equine version for her horses.)  Our dogs on Connectin and Fresh Digest (digestive enzymes by the same company) have stayed in surprisingly good shape and lived well beyond their life expectancy.  Other dogs I know who are on it are also quite healthy.  When we run out of it our senior dogs seem less comfortable.  Success with just a few dogs is not proof of anything, but I'm a fan of this stuff and think it contributes positively to our dogs' health and lifespan.  BTW, if you shop around a bit on other websites you can sometimes find it a little less expensive.