The last ordinary evening somewhere often becomes important only afterward.

Last times are almost never announced. The final ordinary evening in a flat, a town, a job, or with a person still nearby passes as one more evening, and only later takes on the weight of having been the last. That is why so many of the memories that matter were unmarked when they happened. Nobody was failing to pay attention; the information simply was not available yet.

You cannot identify them in advance, and trying would make ordinary life unbearable. What you can do is be a little more present in the evenings that feel like nothing much.