Yes, you can take painkillers for years. I speak from experience. (Oh, and by the way, I can also speak to your experience of doctors getting a clue... I suffered agonizing pain from September to February, being treated for everything BUT the cause of the pain, which was found to be a tumor in my spine when he finally ordered a CT scan...) It's been 7 years since then. Thank God the tumor proved to be benign, but it left me with nerve damage which causes chronic pain from my back down to my toes.
I am not getting the same level of relief that I once did from MS-Contin and hydrocodone, despite steadily larger doses, so I am considering a switch to methadone, which I'm told will give me a better quality of life. It will certainly improve my wallet's quality of life! Methadone is MUCH cheaper.
So the bottom line is yes, you can stay on painkillers for years. It may take some juggling to get adequate relief, but it can be done, and new pain drugs are being tested every day.
Good luck!