Interesting. It's just not what I'm finding, though, as far as the tolerance. It seems to me if you just keep the dosage low then you can keep rolling. If you get overly aggressive and take a half gram at a time or something, then you're going to get a tolerance. Take a few days off, though, and it'll go away.
This article is the best I've found, btw, summarizing the actual major studies done on MDMA and putting it all in context:
http://thedea.org/neurotoxicity.html
I'm really partial to MDA, actually. It's much more psychedelic. I'm fortunate to have some good "sassafras," they call it, at the moment.