It was unspoken early in our relationship. Honestly, it almost never came up then because with two adults, we got stuff done and then were done. The first time I actually remember articulating it to Hillary was sometime after Paige was born. This was almost certainly within the first year of Paige's life.
We had guests coming over in the next day or so. We probably had piled up some laundry. The kids were down and I had finished cleaning the kitchen at something like 8:55pm.
I remember Hillary mentioning that some other chore had to be finished that night. We were both exhausted and sleep deprived. I basically told her that I was done for the night and needed to sleep. We could address whatever needed looking at in the morning and do damage control.
She was not amused. I felt guilty but got ready for bed. Hillary joined me shortly thereafter. We cuddled and passed out almost immediately.
The next morning I actually articulated my internal rule as we did whatever else we needed to do. "I need to have a cut off time of about 9pm for chores. After that I need to be winding down or I'm going to have trouble sleeping and I can't do that."
Hillary's lists were always difficult to complete and over time, I mostly treated them as aspirational. There was, of course, a hidden priority to each item that was occasionally communicated. That particular night, there were some high priority ones that had not been addressed.
After this though, we mostly did it. Rarely were we doing chores after 9pm. Almost every time that it did happen was due to special circumstances. Wrapping presents before Christmas, Hillary finishing a birthday cake late, late into the night, packing for a trip, those sorts of things.
Some chores did get punted to the next day sometimes. I know this particular thing irked Hillary to some extent. She tolerated it and we nearly always went to bed together.