Lizzy, you are the last person on the PLANET who is going to have ANY problem with addiction. Don't even move that "worry" to the bottom of the list -- rather, take it OFF your list!
You mentioned "dependent." That is a "buzz word" that lots of people throw around. As I see it, YOU are the one MAKING USE of the Norco, which is how it should be. IT is not using you, rather, YOU are using IT. So, that list I just mentioned -- yep, you guessed it -- take that worry OFF your list!
You have pain. Norco is the medicine for pain. When your pain goes away, you'll throw the Norco away. Simple as that. Stop worrying.
Now, onto your question "how long" will your pain last.
Here's an "image" for you to keep in your mind. Like, a "mental picture," for you:
Let's say you cut your thumb really bad. Have you ever done that? Not just a paper cut, but I'm talking about a bloody mangled accident, like when a screwdriver slipped, or when you were a kid and you fell of a branch, and your knee looked like it had been run over by a train. Remember that? How long did THAT take to completely heal? A day? No. A few days? No. A week? No. More likely, about 3 months! And that's for an external bang-up-my-knee or cut-my-thumb accident.
So, what you do is think "Okay, it takes 3 months for a bloody finger to heal, what is a reasonable amount of time for intensive back surgery -- oh my goodness... what was that word you used.... a "Cleaning," of your spine? Gosh!
It's time to stop watching the clock!
You were smart enough to get into physical therapy. Good job. You are already smarter than all those doctors who 'forgot' to mention that.
Lizzy, you are on the path to getting totally well. I'm not the least bit worried about anything you have said. Do everything your nice GP tells you to do. And, remember remember remember.... slow and steady wins the race.