I think it probably depends on the person who's doing to smoking, MedusaGrower, more than the amount one has to smoke. It's true, most folks don't smoke more cannabis than cigarette smokers smoke cigs, but I suspect cannabis smoking ages folks more quickly even in lower amounts (just like cigs do) because it does what you said. It depletes oxygen, is desiccating, adds in the byproducts of combustion, which are the most detrimental ingredients in smoking cannabis and the ones that do the most damage (unlike cannabis or its active ingredients itself). This is, to me, yet another reason to vape because I've seen numerous links to information about the beneficial, anti-inflammatory, healing properties of THC and CBD.

I knew two guys were seriously heavy cannabis smokers. They both looked like old leather purses by their mid 30s from that heavy smoke ingestion. It had also dried out and aged their vocal cords in their windpipes, too, because they had that cracking, aged-sounding vocal quality, too, and wheezing from the long-term lung irritation. They were super-heads, though. Not your casual social tokers. They weren't cigarette smokers, either. They might also have had bad genes for aging, as well. That's the factor that determines how someone bears up under environmental stresses more than anything, at least in my opinion. Genes and history of sun exposure.