Have you ever had dead-men-walking insomnia?

Rarely. My usual problem is that I wake up in the middle of the night and I feel completely awake as if I just had coffee, so naturally I can't get back to sleep...

Yes one time that I remember was the first time I ever made green tea and drank it, it was about 1 in the afternoon. I could not sleep till 4 a.m. and really tried to lay down and sleep. Green tea raises the alpha brain wave levels which makes for relaxed concentration which is ideal for studying or creative endeavors.