I felt that it was laid out fairly well in this essay. They described their 25 year rule, and described a lesson they learned in the first 18 months of their company from a few attempts really wasn't working for them. Because they learned this lesson early on they refused a client's request because they were confident in the lesson learned not providing the right kind of value for their organization or their clients. Their rule biases learning from early things that don't work so that they can focus the most energy on things that are working.