Sleeping through the night?

While the Monkey Mama was away for work travel, the Monkey appears to have started sleeping through the night. For two nights in a row, he went down at 7pm or 7:30pm...and didn't wake up until 5:30am.

That rocks.

Here are some theories why:
1) He knows the Monkey Mama is not around, so there is no reason to wake up. ("Wake me when I can nurse...")

2) The days without the Monkey Mama are more stressful, and therefore more tiring.

3) Small tweaks to his schedule -- a late afternoon walk, a late feeding, etc. -- have pushed him into a new sleeping equilibrium.

4) Because he is so hungry at the end of the day, he takes an enormous bottle (9 oz - 11 oz) at bedtime; normally, he falls asleep in the deepest comfort before taking so much from the boob directly.

5) He is actually waking up throughout the night, but the Monkey Daddy is too sound a sleeper to notice.

My best guess is a combination of 1) and 4), with 3) possibly helping. I discount 2) and 5) entirely: he has been having great days with me, and I know how to wake up when it counts (like a crying baby in my charge).