Once a week is sustainable in the short term but I am not recommending that and make no claims as to its safety in the long term. I would have no way of knowing other than googling studies.
That being said I'd still like a source for the claim:
"Yes but MDMA specifically will mangle your brain after very little recreational usage relative to almost all other drugs."
I've known a person or two that simply didn't know how to space out their use, and did wind up with depression as a result. But this is the sort of thing that you can teach so long as you are honest about the rest of your drug education. It is something you can teach when you sell it to people. You can limit what folks can buy and keep a record of when people buy it - we already do this with some decongestants, after all. It isn't that there is not risks, but your comment is misguided on what constitutes more common recreational use of this particular drug and the things we can do to avoid this situation.
Would you prove that please?