[chimeracoder]

> In my party days,I always understood MDMAas being pure MDMA while X was MDMA mixed with coke, meth, or heroin to make the drug effects last longer, as the half life of MDMA is smaller than those other three.

This is a common misconception. MDMA is often presented as "pure" (often by the people selling it), but in reality, almost all MDMA outside of a pharmaceutical setting is impure. Most MDMA contains some amount of methamphetamine[0], but not necessarily enough to be subjectively identifiable by a user as "meth".

Also, the half-life of MDMA is longer than cocaine, but shorter than methamphetamine.

[0] MDMA is actually a methamphetamine, but it's not the one that people are referring to when they say "meth" colloquially.