Ebola? (forgot to Quote your post on MDMA) I'm no chemistry expert, but I've done my experimentation phase with MDMA, and unlike many other drugs I've abused (pretty much anything that can get me high), I never felt the need to abuse MDMA; It was a drug to be respected IMO, using it constantly is pointless; when you're up, you're up, when you're down, it's damned hard, if not impossible to keep the rush going. Many of my pill-using friends were the same way, using the drug moderately, and these lot would tear the arse out of anything psychoactive. Also, the magic phase doesn't last forever; I've used MDMA roughly twenty times - taking it now doesn't give me that I-love-the-world euphoria I wish I could relive sometimes. When it's gone, it's gone, unfortunately.
That's not to say there weren't one or two "hardcore" users who tried to keep the rush going forever; they couldn't do it, of course, and wound up dropping for days on end, failing to stay up, and winding up with two-month comedowns from hell, swearing to never touch the drug again. So, IMHO it's a drug that demands respect; as you said, using it daily for a long time will have serious, irreversible effects - but it's a drug that almost doesn't want you to use it in this way. I've even heard MDMA described as sacred - that's going a bit too far for my tastes, though
Btw IMO there is great therapeutic potential for MDMA; in fact, I read that it had excellent success rates in treating PTSD among veterans returning from Vietnam. It had serious potential to treat many other psychological disorders, too...but of course they banned it, making any future research into it's medical value impossible.
I'd say my MDMA had therapeutic, as well as recreational benefits, as well; for weeks after taking it, I experienced increased confidence (I suffered from low confidence as a teen), increased empathy towards others - and that was a big thing, I was at a very self-absorbed age, and improved happiness in general, including relief from depression.
I agree daily, even weekly, use would be unsustainable for therapeutic purposes. This is a drug of moderation; perhaps monthly use would be appropriate?