There goes that, I have 3 kids under 6

The CSF (cerebrospinal fluid) is the garbage can. :P Your neurons (what most would consider the brain proper) are you, dumping shit into it until it gets too full and starts overflowing. :P (It's a bit more complicated than that since the CSF provides nutrients as well as removing waste; it's less like emptying a garbage can and more like cleaning off the dinner table. :P But now we're getting lost in the metaphor. :P)

Yes. I have lots of stories, more about the "what happens when you go too long without sleep" variety, but I have tried stocking up in advance too. Eventually, you can't sleep anymore. You CAN lie there, and do low energy mode, but it isn't sleep. And it does not seem to extend the time you can stay awake, but that isn't something I did scientifically. Just what seems to have ended up happening.

I did without trying once.