I've been high enough that it lasted more than a day. I smoked Blueberry Haze, and lots of it, from an extremely reliable dealer. Wasn't laced. I contend that it IS possible to be stoned for 24 hours, and that it IS possible to get stoned, go to sleep, and wake up baked. That's from personal experience.

I've never been able to sleep while on shrooms or acid, though.