It's all tolerance, people who have been abusing opiates for a long period of time, will need something stronger, every so often. My experience is perfect for this topic.
I started using opiates at the age of 17, I'm 25 now, so that's 8+ years of Opiate tolerance. For the first 2 years, I was taking Hydrocodone Orally doses ranging from 80mg-120mg/daily. Hydro wasn't doing the job anymore, I had to take 150mg of it to feel my desired effects, and taking all that Tylenol could've easily killed me. I will never CWE my pills, for 2 reasons, takes too long, and losing some hydrocodone, So, I switched to OXYCODONE, that came in OC form or ROXY form without APAP, but the problem was, I stopped using Hydrocodone for 5-6 months COLD TURKEY, it was the toughest part of my life, but I got over the hump. My tolerance NEVER went down, I needed 60-80mg of Oxycodone per dose to get my desired effects. That's the problem with opiates, tolerance to them is a mother fucker, never goes down IME, so I was taking oxycodone for 3+ years, after they got too expensive, I tried to quit oxy cold turkey, I went 9 days in of HELL, and after those 9 days, I was feeling WORSE. I was like WTF, because with Hydrocodone I started to feel a little normal after just 5 days. So im like fuck this its never going away, that's when I started to smoke HEROIN, chasing the dragon for over a year, that's 6 years of Hardcore Narcotic abuse, the Heroin W/d was the only one I wanted to DIE on, I was sweating like I just got out the shower, I was puking on a empty stomach, some yellow acid type shit that was more bitter than Xanax pills, I was in extreme pain, RLS, I was literally crawling on my knees, my family saw me and rushed me to the hospital, I commited to them that I was on addict and need help, before we went, so I go in the ER and they put me in a room in less than 30 mins, because they saw how much pain I was in, seeing me puke out POISON, sweating like I just got out the shower, I was nearly about to DIE from dehydration. So they immiedatley put me on IV, started with just water so I don't dehydrate, the doctor came in and saw me in less than 15 mins cuz I was yelling, crying in pain, I didn't lie to the nurses nor doctors why im here, they said this is the only time we can help you with dope sickness, so they gave me meds to calm me down, all IV, Morphine, Ativan, and Promethazine. I finally stopped shaking, and could talk right, I was still in w/d but minor, because I wasn't dosed with enough morphine, obviously. The doctor told me and my parents, the only way to save yourself, is 2 options, REHAB, or MMT. We couldn't afford rehab. So my parents rushed me to a MMT clinic, and here I am today, 2 1/2 years later, still on methadone.
So that's nearly 9 years of using opiates, almost nothing will over power methadone. That's why tolerance is a bitch.
But I thank first and for most, god, and then methadone, because 'done SAVED my life.
Without methadone, I guarantee you I wouldn't be alive today.