By then, you're addicted and need to keep taking it just to feel normal again.

Well, the true steps would be to get to that point - and then move onto amphetamines (heroin tolerance doesn't affect amphetamine effects). Once that blows over, you move onto cocaine (amphetamine tolerance doesn't affect cocaine effects). Once that blows over, you move onto ketamine (cocaine tolerance doesn't affect ketamine effects). Once that blows over, you're tolerance for heroin is back to base and you're good to go again!

Note: Obviously I'm not recommending any of this. I'm just telling you that's how it "really works". At least, for any drug addict with enough money to carousel around the various drug types ad nauseam. The path to being burned out on drugs takes a lot longer than people let on. You don't just build a tolerance for something and go, "Well there goes that part of my life!"

The fact that it takes so much longer than people let on is exactly the problem. It takes an almost impossible amount of strength to undo decades of habitual drug use. It would be much easier if "all" you had to do was undo the single year or two it takes to get to the point where your usual dose of heroin doesn't have an affect any longer.