The recidivism rate of heroin addiction is so high. They can either go on and on until they OD (almost guaranteed), contract AIDS, hepatitis, etc. or go quickly this route. I’d say this route is more expedient.
I've seen a couple of people turn their lives around, but most of the ones even in Narcotics Anonymous (I dated one and met many of his post-use friends) still have the same street values and attitudes.
My main sorrow is for the families, and I don't know whether it would be more painful for them to see the utter degradation of their loved one before death, or an early death when they still had hope (usually false, unfortunately) that the person could turn around.