Yup, I came to the same conclusion. Tried wearing my watch when I slept but had to take it off. Not to mention I had to charge it 3 times during the day so it would have enough juice to make it through the night. Then I got the low battery notification when I woke up.
Indeed, unless they give the next watch a monster battery, that is just unworkable as far as user scenarios go. And even then, it's quite bulky to keep wearing on your wrist.