"We used to talk till three and it was fine"

Early on, you talked all night. Two in the morning on a kitchen floor, working something out, and it was one of the best conversations you've ever had, and you're still together partly because of it. So the late hour can't be the problem. You've done your best work in it.

Two things were different, and both of them matter.

The first is what the conversation was. At twenty-four, on the kitchen floor, you weren't settling a row about a dishwasher. You were finding out about each other, and finding out is a thing the late hour is kind to. Nobody was defending a position. Nobody had a thing from March. The late brain from chapter 6, with its brakes loosened, is bad at holding back a sharp sentence and quite good at saying a true thing you'd have been shy of at noon, and at twenty-four the true things were the point. Now the true thing at half past twelve is about their mother, and the brakes are what you needed.

The second is what the morning was. At twenty-four the morning was a lecture you could skip and a coffee at eleven. Now the alarm is at half past six and there are two children and a job, and the night's cost lands on all of them, and chapter 3's low hour is lower for a person who's been up since half past six carrying a house than it was for a student who woke at ten.

So the memory is real and it isn't a counterexample. It's evidence of what the late hour is good for, which is talking, and what it isn't good for, which is settling. You can still talk till three if you want to, on holiday, with nothing to settle and nothing at half past six. What you can't do is settle a row then, and you couldn't at twenty-four either, and the reason you don't remember failing to is that at twenty-four there was nothing to settle.

If the late conversations are what you miss, and a lot of couples with young children miss them badly, chapter 7's slot is for those too. Not for the row. For the talking. A Saturday morning with coffee and nothing to fix is the kitchen floor at two in the morning with the good bits kept and the alarm taken out.