In 2010, the most notable thing about the Cowboys' offensive line was its age. The 2010 starting line of Doug Free (26), Kyle Kosier (31), Andre Gurode (32), Leonard Davis (32), and Marc Colombo (31) totaled 152 combined years of age.
A few years ago, ESPN's John Clayton wrote about the "Theory of 150", explaining that if the combined age of your starting offensive line exceeds 150 years, you should expect a decline in performance. A combined age of 150 years means the average age of your linemen is 30 years, and as a group, that may be too old:
If a team lets its starting offensive line exceed the total age of 150 years for five starters, the clock is ticking on its remaining success.