NFL players usually get three contracts in a career if they're really good.
Rookie: 4 or 5 years (dependent on round selected)
2nd Contract: 3 to 5 years
3rd Contract: the "twilight contract."
Usually by the time someone reaches the end of their 2nd contract, they're around 30 years old. Some players are older, depending on if they get intermediate extensions during that 2nd contract (like a Brandon Carr); you should always be wary of the market for guys who are 30+ looking for a big pay day in that 3rd contract. Stephen Jones seems to be mentioning that philosophy, and it helps keep your team young and on budget -- unlike before Stephen took the reins, when we gave out huge money to guys pushing that 3rd contract like Marion Barber, Leonard Davis, and others.