The arrival window, counted from the agreed hour
Forty to sixty minutes from a confirmed hour to a knock at your door, the same figure in every central district and at every hour of the day.
The arrival window is the gap between the moment an hour is confirmed in the thread and the moment she is at your door. In central Amsterdam it is forty to sixty minutes. That figure does not move for the district, the day of the week, the hour on the clock or the weather.
Reading a booked hour correctly
The hour written in your confirmation is the knock, not the departure. An arrangement at half past nine means half past nine at your door. Couples planning an evening around a late second landing get this backwards more often than anyone else, and the consequence is either an hour of standing around or a rush through a shower.
What lengthens it
Three things, all of them on your side of the door and all of them avoidable. An address that arrives late, because the window starts from a confirmed address rather than from an intention to send one. A street door, lift or entryphone that nobody mentioned. And a phone that has gone silent at the bottom of a bag. Ten seconds of typing in advance covers the first two.
Schiphol is a separate conversation
A room at an airport hotel sits outside this figure. It is arranged separately and the journey time is agreed with you before the booking is fixed, rather than being quoted as a window. Couples with two early flights on a last morning sometimes take that route, and it is worth raising in the first message rather than at the end. The second arrival is what the whole timing should be built around.