Certainly engineers have created robots that have gone farther than the PR2. NASA's Mars Rover? That has Willow Garage beat thousands of times over. Yet the PR2 is both more practical and more accessible. The techniques used to keep the PR2 running autonomously are available to all robot developers through the open source ROS software library. There are now 16 different groups around the world developing the PR2, and many more using ROS. PR2 developers can write code for the robot that takes days, or even weeks, to finish and remain confident that the bot can finish the task. The PR2's marathon session is just a tiny step in the grand history of robotics, but with the connectivity of the open source community it will be a step multiplied many thousands of times.