In case you don't know, a more easily-attained big accomplishment is called the metric century. It's 100 km, i.e. 62 miles. 62 to 75 miles is my favorite length for a long day's ride. After that, I get pretty desperately tired. I do it to say I did it or because I'm with people I committed to riding with. If I could convince my fellow century riders that we should do a metric century, I'd be happy. Once, I met rhm after he had ridden a few miles, and I got back to my car after I had ridden about 100 km. He went on, and by the time he got home, he had done 100 miles, so we got to satisfy each of our itches.