I'm not sure what a full day visit to the Lake Tana monasteries and churches involves, but the half day tour (3-4hrs) is pretty skimpy. We visited 3 monasteries, the blue nile (which is just a place in the water at the far end of the lake), and Hippoland (which is a rip off because apparently the Hippos are only there for a short period during the year, but they sell it as a sight to see all year round - meaning you go see a tall grassy area and you see no hippos). All of the monasteries look alike and women are not allowed in all of them. The cost to enter each monastery at this time is 100 birr pp. It probably didn't help that I had a crappy guide who literally knew NOTHING about the monasteries. So, as these places didn't offer much visually, if you do a half day ride, I would highly recommend getting a guide who is knowledgable about the history so at least you can learn something on your trip.