i know what you are talking about i had the same thing done about 5 years ago .. i just went to the dr on the 13th of nov and they told me that the place they worke on in my back is doing fine.. so i ask him then why iam i in so much pain .. i mean when i work more then 4 hours at work (which i do most days) iam in so really bad pain when i go home ..dont know about you but iam getting all kinds of pain in my leg and arms mostly on my right .. it gets so bad at times iam draging my leg along .. not a pretty thing to see .. so iam not sure how long it last but i really dont thing we get in real relief from anything we do ...
My ortho told me that on average your discs above and below your fusion last about 10 years. He said he had printed a journal study on this. I got about 16years out of mine. So far I am not getting any relief from anything. Currently in PT, which hurts, and seeing a pain doctor. I lived a very active life just 2 months ago. Now I can't move for I am in pain. Your in my prayers.
Go see a pain management specialist or a physiatrist (not psychiatrist). You will be happier, and more functional with less pain.