I once hadn't slept the entire night, but then fell asleep next day at about 5 PM. It was one of the only times that I woke up because I wasn't tired anymore, not because something woke me up. I woke at 4 AM feeling totally refreshed. Since it was still night, I decided to try to WILD. It was amazing, because it was very successful - I went in to a lucid dream almost immediately.