Originally posted by Gwendolyn
Your brain never really shuts off. It's running all of the time, constantly. So, why would being able to control your dream make it any more tiring?
I'm no expert on brain activity, but I would guess that whilst sleeping it is less intense than whilst awake. So my thinking was that during an LD you are somewhat halfway between a dream and reality, so brain activity is going to be similar, i.e. involving more of it because concious thought is required.

I guess I'm not gonna wake up knackered then if I do a marathon in an LD