Physical dependence is probably the most realistic "health concern" for opiates.
As torturous as withdrawal is, we quickly forget how shitty it feels to sweat like a pregnant woman giving birth, yet cold.
Some street opiate addicts are commonly portrayed as emaciated toothless Bloodborne pathogen-having prostitutes. This species of street level users are very common, and this isn't from opiates but I'd say rather from social class. People of low social classes who aren't drug addicted often look like they are in poor health as well. On the other hand, there are addicts of higher social classes who appear to display perfectly healthy and normal lives. Very commonly Doctors, go figure.
So no, opiates aren't really too harsh on your body, unless you become physically dependent. This developed so quickly for me from IV heroin use that I almost always asked myself I was just imagining it.
Your CWE'd codeine probably isn't too much of health concern, although I know it's kind of inconvenient having to extract the shit. I would suggest moving on to a opiate-only containing pharm...actually that might not be the greatest idea. I highly doubt you'd still want to extract codeine by the time your tolerance triples though. Codeine has pretty much no value whatsoever to me, so enjoy while your tolerance allows! I remember how great I felt from the Tylenol 3's back when I was completely opiate naive.... it's funny how now I can smoke a 2.5 mg patch of fucking fetanyl in one sitting and feel very little of that motivated opiate euphoria and instead a slight buzz followed by a nasty next day hangover that wasn't even on par with the buzz I received.
but anyways, before this turns into a novel...