Well I have been using it for my 12 yr old GSD and I do think he seems a bit more mobile and cheerful than when I have just used glucosomine. Warning: it is very GREEN. Out of the jar it is a dry powder with chunks of things in it ... so I usually add a bit of warm water or warm chicken broth to make the powder more appetizing (thats very human subjective I know) with his dry kibble with a bit of meat or canned added. We had a week where he stayed at another house and forgot to take the longevity... and I think he seems better on it than off. Its only been a month or so for us though. I plan to get more.
I have been using the Longevity and Bug-Off for both my dogs. Started with Kayla before Lancer came on. They do real well with it and seem to really like it, but then I haven't found anything they won't devour yet. I also add about a half cup of warm water with it and the dry kibble. The green is due to the chlorophyll that is one of the ingredients.
I just started my guys on Longevity a couple weeks ago, so I don't think it's been long enough to really see the effects, yet. Gunner's coat seems to be a little softer, but that's about the only thing I've noticed so far. It's certainly not causing him any problems, so we're going to stick with it and see what happens.
It didn't agree with my Golden. We started out slow, like they recommend, with just a sprinkle. But once we got up to a full scoop, the loose stools started. We stopped it and he was right back to normal, so unfortunately there's something in it that doesn't agree with him. We might try it again, in case it was something else or just a fluke. Haven't decided yet.