We are also considering a Viking Cruise. I have been reading the included excursions, and many of them say at the end, "You will then return to your ship." The longest of those is four hours, and it made me wonder if we were required to return. The only cruise we have ever taken was in 2005, which was an Alaska cruise-tour with Holland America, so I am clueless! How long are we allowed to stay in port? I assumed it would be pretty much all day.