Impressive. A thread where every post so far (save by one poster) has been deemed, "Dangerous, Irresponsible". Glad to be here!
If you want to consider weed as an herbal it makes sense to treat it like one and not burn it and inhale the smoke. I would agree that doing that can probably never be good for you. Given that it's a mixed bag of components and fairly easy to do targeted extraction, there's no reason to ingest any one component known to be toxic. Most of the literature I've seen suggests the CBD component is the main one with the positive health effects and no downside. The good news is it's now generally available in 98% and higher purity but not yet as widely studied as I like to see.
Howard
You've got a point about smoking, as none of the people that have inhaled cannabis since about 3000BC are still with us. That has to say something about the longevity angle. There does deserve to be far more studies done on cannabis. Of course it's all the harder when doing even basic science on cannabis is often resitricted. It's so engulfing in political, legal, and availability issues.
Like other herbal substances, more mundane uses for pain, nausea, and nural aliments seem more promising and will get funding. I ran across this, 60 Peer-Reviewed Studies on Medical Marijuana, but alas no mention of longevity.