I have done that a lot in the past to establish a baseline. I know that if I take that baseline and adjust it according to temperature, checkpoint weight checks, and observations like urination frequency I will get things pretty close to what I need.
16 - 24 hours depending on the amount of vertical in the course and quality of the trails. Overall cutoff times for most 100s are either 24, 30, or 36 hours.
I am not sure what you are trying to argue here. Sure it does not make a difference which container you got your water; water is water. People have different ways of keeping track of how much they are drinking. Some people use Camelbaks and I would assume that is what works best for them. I use bottles and I prefer them over hydration packs for some events that I do. For hiking, back packing, mountain biking, and warm weather climbing I prefer CBs.