I am away from Atlanta and on my cell phone - sorry for the brevity and any typos.
I do not see how a doctor can tell how long anybody will have tinnitus. It is true that the longer you have it, the less likely it is that the tinnitus will spontaneously resolve - especially after a year or two - but I know of cases where it has disappeared even after five years! And even when it doesn't go away (many many times it does!), in most cases folks find that they can quite successfully accommodate to it. Moreover, there is a lot of ongoing quality research towards a cure. So it sounds to me like you went to your doctor feeling bad ... and you left feeling worse. For no reason at all that I can think of!
As far as the second issue you raise in your post, to the best of my knowledge chondroitin and glucosamine do not cause tinnitus. I am attaching an article about "Drugs To Avoid" that amplifies my views on this subject.