I started giving my whippet Rickie Cosequin DS (now Flexadin here) in 2004 after partial carpal fusion surgery in one leg, as one of the long term side effects is arthritis. Rickie turned 10 in June, and this fall developed a limp. Had the leg x-rayed, there is arthritis. I like to think the arthritis didn't set in sooner, or worse, because of this supplement.
I have Metacam but worry about it for long term use. Consulted a trusted holistic vet - he recommended Wobenzym and Zeel. They can be used in conjunction with all the other stuff.
So our current protocol is Flexadin, Metacam (I am weaning him down from the standard dose to 1/2 and then 1/3 the amount) and we just started the Wobenzym and Zeel, so it's too soon to say. If he improves sufficiently I will cut out the Metacam altogether for now.