Interesting. I've been wondering about that too.
I've been averaging 1L in the morning, another in the afternoon, and one at night, with a glass or two in between. I might change that though and not have any at night, with the mentioned "OMG I have to pee at 2am" happening to me
Currently, since I'm only a week into drinking all this water, and it takes me awhile to get into the swing of it..I find it easier to drink it all at once from my bottle. Like, I'll down 1L in about 20-30 minutes and leave it at that for awhile. I dunno if thats great to do either, but its working for me so far