We have never stayed overnight in a port. The closest we have come to it was in Hamburg. We left about 2300. That was fine as we took the train to Berlin for the day and were able to see some of Hamburg at night.
I think that is OK, but not a full night.
SS Norway (12 times) '85 - '97; Radiance OS 06/01; Island Princess 11/04, Grand Princess 11/04/05, Golden Princess 7/21/06, Golden Princess 2/24/07, Explorer of the Seas 12/23/07, Island Princess 11/15/08