TL:DR You can't be a functional addict.
This is what I was going to say(In regards to jesuss_son). It's pretty much inevitable for anyone. Even if you are going on ten years chipping and maintaining your rules you are still susceptible to it getting out of hand.
However since you asked I have been an addict for about 5 years now. I was off opiates for about 4 months around the 3 year mark. Prior to that it was at it's worst(shooting H daily, not holding a job, unstable relationships, and no permanent residence) but since then I have managed to keep a job and pay for an apartment. I also have met and been living with my girlfriend since then who does not use opiates but is aware of everything. She does take the occasional 5mg percocet once every few months when her cramps are bad.
Things are good and stable for now and some people on a pipe dream may call what I started doing "successful chipping" at first. I began taking Hydros after being clean because this guy at my job had them so readily available. I was good about it at first never using more than one day without another day in between. And also during this time I recall pushing away the thought of me knowing it was a relapse like any other. I only thought about how eating a few hydros is wayyyyy better than shooting H again. So after a few months I naturally was doing them everyday that he had them, and developing the bad habits of annoying the guy a bunch even when I knew he likely didn't have any at that moment. I really didn't want to resort to contacting old friends and dealers. Cold copping was never one of my faves but I have pulled it off a few times and I knew I didn't want that either.
This period lasted another month or two before I ended up contacting a guy I used to get blues from when there wasn't dope. So fast forward to now and I've shot blues more than several times since then and H a few times when I caved in and called someone who was convenient (got burned for 70 bucks on one of those tries). I go for 5-6-7 days at a time without doing anything, but always end up on a multi week binge at some point. I know i'm a few bad months away from losing everything and it doesn't bother me too much to honest. I actually rarely post things this long or comment much at all. I think what drove me to share was the thing in everybodys head when they read this "There aren't any real functional addicts".
Btw I am 20 y/o male and my gf is 25. I work in a fairly nice restaurant kitchen where I make a few dollars over minimum wage. Nobody other than my gf knows the severity of my use or that I shoot.