I'm not sure about taking it the night before, in anticipation of a poop-a-thon. I usually wait until the a.m.
I totally completely understand. When I was in University, prior to diagnosis, I was exiting to use the toilet at least twice per class. I recall, when I was a barista, I lived with neverending D, but then I was drinking exclusively coffee or beverages with high fructose corn syrup that are known for explosive resposes (okay, Coke or diet Coke!) and fruit juice on an empty stomach.
I suppose you could do an experiment or take a poll. I generally wait until the a.m., though.