One of the most important factors when deciding which cruise to go on is how many hours I spend in port. I do not want to get back in time for an early supper, but would rather stay on land until the sun goes down (8-9 p.m.) so I can take my time and not be hurried or miss out on some things.
While looking at scheduled European itineraries, I checked departure times and noticed they are too early for me. Is this the norm or does Princess often leave ports later than 5-7 p.m on Mediterranean cruises?
It depends entirely on the itinerary. Some ports, like Livorno for Florence, or LeHavre for Paris, the ships stay much later because of the time necessary to get to the "major sights". Ships often overnight in Venice, where that's included in the itinerary.
If you look at some of other lines, I think Azamara Cruise Club, and Oceania are now featuring many more overnights, and longer stays in ports of call.