Ever have a night of dreamless sleep?

I'm thinking that it must be becuase I'm not getting enough rest and I'm really pushing myself to the limit of my ability. Perhaps Nietzsche was right? If we only have a certian finite amount of energy to put into our day to day, then even while we are asleep, some energy must get used up through dreaming, right? I guess if I'm really that exhausted, I won't dream. Do you dream if you're exhausted?

Sno