That is the same conversation I had with my vet after Phoenix was diagnosed with osteo and he said almost the exact same thing. Luckily he confirmed what I was already thinking. Osteo cannot be treated, unless you go the amputation/chemo route, which has been successful for several hounds here That route isn't always feasible and / or some of us have reasons for not doing it. My feeling was that if you have to raise pain meds, you're not really doing the dog any favours. You may have some more time with him, but who does it benefit? Not the dog, who is probably in pain regardless of meds. A dog with osteo is going to experience huge amounts of pain. I couldn't do it. I know I'm in the minority, but for me letting Phoenix go at the first sign of extreme pain was the right thing to do. I miss him terribly, but I know that he never had to suffer again.
I don't mean any disrespect to those who increased meds and gave their dog cocktails. We all do what we think is right.