Change is the only constant in this life... If you're not working on getting younger you are undoubtedly getting older. If you're not working on getting leaner then you're probably getting fatter. If you are not working on improving your fitness than you are by default losing your fitness. Change will drag you down unless you work on directing its course.
You don't necessarily have to quantify change to know which direction your moving but it's always fun to see progressive metrics. Kudos to the HardCore athletes who defied the "natural aging process" and actually improved their sustainable power production, cardiovascular efficiency, power/weight ratio, and preferential use of fat as an energy source. Races are a great way to quantify your fitness. There's nothing better than comparing you to you, year after year. Never stop working and never stop changing!