It’s fascinating to me how quickly the “routine” of our (now) four-month-old changes.

For the better part of the last month, L was waking up every morning around 6:30 a.m., at which point I’d take over for Powergirl, play with her in her room and then bring her into town for a trip to the coffee shop and an extended morning walk.

Suddenly, three days ago, the baby decided she needed more morning rest, and has started sleeping until—gasp!—nearly 10 a.m. (it’s 9:15 a.m. as I write this and she’s still snoozing).

For me, the change doesn’t really mean much; I’m still rising early to get work done while the house is quiet. But for Powergirl, who until Oct. 19 is up at least once in the middle of the night to breast-feed, L’s new “routine” means two to three additional hours of sleep—the equivalent of two to three hours in the most fabulous spa on Earth.

What prompted this sudden change in habits? And what did we do to deserve a child who sleeps so soundly through the night? I doubt we’ll ever know the answers to these questions, but it sure is fun to wonder when L’s routine will change again next.