My Basset was diagnosed with subluxation, both hips and his spine -ghastly. He'd been on and off lame before, but the last time, earlier this year, I decided enough was enough and had my vet check him. He wasn't totally sure what was going on but gave him antiinflammatory meds. That evening he was bad enough for me to call the emergency vet who gave him a shot, basically an opiate and he had a reasonably quiet night. The following morning he was pretty bad and I took him back (was going to anyway) and my vet had him walk up and down outside the office. His movement was quite frankly, alarming and we were both surprised at how rapid the 'deterioration' was. He was admitted for x-ray which is when we found out what was going on. However, thinking back later, I honestly believe the deterioration was down to the evening drug he'd been given still being in his system. He was given pain relief tablets (I forget what) and Metacam. Eventually he was able to come off the painkillers but kept on the Metacam, dose as per his weight. Since then, and it was some months ago now, I've been gradually reducing the amount he's given, and having seen the vets last week to discuss what should be done, much as I bought another large bottle of Metacam, it was suggested I took him off totally and 'see what happens'. He's been off for 3 days now, and is apparently fine. He's 7, 8 in October. And obviously much as it was said he may need to be on Metacam indefinitely, I really don't want him on it any longer than needed. Some vets will do a blood work-up at some point if a dog is on this long-term. There was no suggestion my boy needed this - and he has been fine on it, no bad stools, lack of appetite etc.
I think you can only be guided by the treating vet. Just my opinion.
ps This boy presented with premature closure of the growth plates early on (around 9 months when he again was lame) and at the time I was warned about arthritis later on - his ulna both sides, was affected. Basically the boy just grew too fast (I bought him at 4 months and at that time he was a very big puppy). At one point he did have a couple of courses of acupuncture, which clearly helped.