I like to run 40 miles a week. I check it in my watch and write it down in a calender to double check my math and see my totals for my self. Some people keep track of their running by time and that works too, to each his own.
Recently at the running store we have started a competition among the employees and group runners to see who is running the most miles for the year. Obviously some people will run a lot more than others. The competition is just meant to be an all inclusive way for people to see their progress and hopefully inspire others to how many miles they can do as well.