Cocaine and mephedrone are the only drugs where I've frequently finished my entire supply, even when the supply represented a clear excess of a reasonable amount. I'll find myself starting to feel really shitty and strung-out, but I'll still torch my way through another 4 grams of base when if it was someone else's coke, I would turn down a hit. However, this was partly due to some foresight on my part, which I then threw out the window with mephedrone. I would force myself to finish the blow in one sitting, because from experience, after doing any more than a line or two of blow, I will have cravings the next morning. If I have cocaine, I'll give into the cravings. If I do that, the third day I've inexplicably felt like God damn - I
NEED some blow.
It was much more of a fiendish "Must reinstate highness levels still being felt 5 minutes ago" desire to redose with mephedrone though - the comedown from a single dose did not bring about any of the typical symptoms I associate with a comedown (though they came down with a vengeance with repeated dosing), but instead, you suddenly realized that you feel almost sober and normal, when literally seconds ago you were on cloud 9. It's not so much a "crash" as it is a teleport straight from the high stratosphere onto the ground . Redosing yielded a nasty comedown when you finally stop redosing (I usually stopped by running out of drugs), and the euphoria from the second dose felt diminished even with much higher doses, but it was still worth it redosing, every fucking time.
That shit doesn't seem too healthy, nor did it feel it, and I'm not going to touch the stuff again. But for the brief period while I used it, I would invariably exhaust my whole supply in a decadent binge. I was slightly disillusioned when I first tried ecstasy and it wasn't all it was cracked up to be. When I tried mephedrone, THAT was the feeling I anticipated from ecstasy. A forceful, overcoming sense of euphoria that constantly felt so good that it almost made me sick.

Kinda scary, good thing I didn't go through too much of the stuff in the end. No other drug made me scream "Fuck work tomorrow/the chance of the cops coming/all of common sense, I'm having more!"