I agree with David, too. Not that I would quit cruising, and in fact I dislike being in the same place for too long.
But I definitely do like overnights, especially in great ports.
To me, some ports deserve more than one day and some don't. I love seeing Athens, but I don't want more than one day. But to see Venice or Rome you need at least 2 or 3.
Personally, one day in Florence/Pisa is enough for me.
In the Baltic, I don't need more than one day in Helsinki, Copenhagen, Stockholm or Oslo. They all look the same to me. But St Petersberg is 3 or 4 days needed.
I do want to go to Europe some day with a Car and spend as much time as i want anywhere I want to go.