How Long Can Morphage Intake Help Cure Back Pain And Nerve Damage?

I have been on morphine for the past 10 years and have started to cut back on my own. I have been taking the extended 15 mg one am and one pm. I have also been taking 30mg immediate release up to 3-4 times a day. All of this prescribed for chronic back pain and nerve damage. How long should I take to wean off? I have already stopped the immediate release down to once a day in the am. Pamela