How long do dopamine levels return to normal after stopping opiate use?

If we only knew,: That is one of the most important questions in addiction medicine--how long until i feel good again? I think that if we knew the answer to this question for everyone, drug addiction would be much easier to treat-- simply because you would know exactly how long you will feel withdraw. It's the not-knowing that makes it so hard b/c you don't know when the end is. Makes it much harder!