Hmmmmm, I don't know if it's coincidence or the fact that BootSpeed puts that run-once entry in the Registry, but it seems like every time I go to time my warm boot using it, shutdown takes twice as long as normal(subjectively seems that way anyway.)
But Curt, if you use BootSpeed that's all it times is a warm boot. It sticks the entry in run once and stores the timer tick, then subtracts the timer tick from the current one when it opens on reboot. I haven't really looked at the code to see if it accounts for passing midnight or any of that. But the time is measured from the moment you click it until it comes up after the warm boot.