The most unusual recent explanation for a congressional retirement is surely Bob Walker's. Walker, the 10-term Pennsylvania Republican, put it this way on Dec. 15: "Since the first Continental Congress 220 years ago, the Pennsylvania Dutch seat has established a proud tradition. Part of that tradition is that no one has served for more than 20 years. As someone who came to the office promising myself that I would not spend the rest of my working life in the Congress, this is the right time to move on and in the process help keep a little bit of history intact." Wow -- Amish term limits!