This weekend, I noticed something interesting while we drove to Squaw Valley and back. I wanted to enter all of the places that we were going into the navigation unit, so we wouldn't need to add them again later. Also this would allow the navigation unit to calculate the best route between all of the destinations.
After I entered five destinations, I was not able to add amy more. It looks like this limit is in the software itself. Maybe it is too expensive to calculate the best route between more destinations, but this limit seems pretty arbitrary.