A lot of NFL players who have been around as long as Charles Tillman accumulate a wealth of knowledge that makes them more effective.
The problem is, that after 10 years, the mind and heart may be willing, but the body is no longer able.
Tillman is different.
He's playing the best football of his life at age 31. Last year he made his first Pro Bowl.
He's obviously still growing as a player -- literally. Since he entered the league as a second-round pick out of Louisiana-Lafayette in 2003, the 198-pound Tillman had always been listed at 6-feet-1. This year the Bears' roster says he's 6-2.
"I've always said I was 6-2," he said.
Lately he's been playing even bigger. He's been the NFC defensive player of the week in each of the Bears' past two games, most recently for shutting down the Lions' 6-foot-5 Calvin Johnson.
Tillman is smarter, more experienced and plays with better technique than he did as a rookie, when he became a starter in his first month in the league. But he admits he's lost a step -- or maybe a half-step.
"I might not be that 4.43 (in the 40) guy of 10 years ago," he said. "I might be maybe a 4.5. But I think my technique has gotten better. I think I've gotten a lot smarter. I think I understand the game a lot better than I did a few years ago."
Tillman is smart enough to realize he doesn't know everything.
"I don't have cornerback figured out," he said. "I've made a lot of mistakes playing this position, and it (stinks) when you make those mistakes. But I've learned a lot from my mistakes in years past.
"Each year I learn something. I learn something more about the position, I learn something more about myself. With each year there comes knowledge. I'm always trying to peak; I never want to level off. Each year I want to get a little bit better."
Middle linebacker Brian Urlacher has been in the same starting lineup as Tillman for each of the past 10 seasons. He believes the acclaim that the cornerback is just now receiving is long overdue.
"Peanut's awesome," Urlacher said. "I don't know if he's gotten smarter or whatever, but he's a great player. Maybe he feels like he's gotten smarter, but he's been the same to me all the time.
"He's always been good. He just hasn't got the recognition. He's been taking the ball away his whole career, but there have been some good corners in the NFC and they've kind of overshadowed him."
Tillman has forced 32 career fumbles, more than any current defensive back since 2003. Among all players, only Colts defensive ends Robert Mathis (38) and Dwight Freeney (34) have forced more. Tillman also has 32 interceptions. Since 1991, he and Brian Dawkins are the only players in the 30-30 club.
"I don't know if he studies film better or what, but he knows where to be, where to fit," Urlacher said. "Even in the running game, he's coming up and supporting the run a little bit, too. But he's always done that."
Tillman's toughness against the run has been a constant for a decade. Six times he's finished third on the team in tackles, usually right behind Urlacher and Lance Briggs.
"His tackling is excellent," said Bears defensive coordinator Rod Marinelli. "He's as good as there is in the game."
Despite his rugged style, Tillman has missed just six games in eight seasons, and physically he appears as good as ever. That hasn't happened by accident.
"Just knowing my body and taking care of my body a little bit more," he said. "Eating better. Getting more rest. Just training differently; taking a day off in practice, maybe not getting as many reps, conserving your legs a little bit for Sunday."
So, even after 142 games -- not including 40 preseason games, which he keeps track of because he despises them -- and 867 tackles, it seems as if time is still on Tillman's side.
"He's definitely better (now)," Urlacher said. "The more he plays, the more he sees, the older he gets, he's just getting better."