I agree with Chris, I had the same experiences.

For the past 5 years or so, I would be narcoleptic every 3 months... I would pass out mid convo, fully dressed, you name it. I would just be lights out.

Since I've tweaked my schedule and incorporated a lazy day once a week, I have rarely had that problem, and when I do, I actually get a warning, I don't just pass out.