We took a 15 day Ancient Med Treasures cruise which is really two 7 day cruises, back to back. It worked out well, with an extra day in Athens. This cruise had a very nice itinerary.
We also added the two day pre-cruise extension in Istanbul. It is really a one day extension, with too much "free time" at the hotel. Even though the Conrad hotel is gorgeous, it's not within walking distance to much and the awful Istanbul traffic meant that we spent much of "day 1" sitting in traffic on the way to the hotel. I don't know what could be done differently, however.... We DID like the tour we did take but it was the only one.
LOTS of walking! Every day brought an ancient site to explore. That was all great, informative, and verged on information overload.