I'm a homer now, so bare with me. I'm really excited about the defense next year, and have always been on the fence with Pace...but...
Can you imagine how people will view this deal if we miss the playoffs the next two years? Did Jared Allen and Julius Peppers work wonders for Minnesota and the Bears? And Mack is 27 years old. We got three years to do something. Most of these guys decline at 30 and hit the wall at 32. And we won't be adding through the draft. This team is what it is THIS year.
If we don't turn the corner and become a REAL Super Bowl contender it's very easy for me to see this deal being considered a historically bad one.
To begin with, it is 30 years when running backs hit the wall. There is no such data for pass rushers.
For your information, I took some of the all time sack leaders and gave amount of years that they had 10+ sacks in their 30th year or above. If your belief is true, they should have a maximum of 2 years with 10+ sacks.
Bruce Smith (7 years)
Reggie White (6 years)
Kevin Greene (7 years)
Chris Doleman (5 years)
Michael Strahan (4 years)
John Abraham (4 years)
Terrell Suggs (3 years)
Julius Peppers (4 years)
Jason Taylor (3 years) your best one - last 10+ was at age 33
John Randle (4 years)
Seeing that Mack is on the right path to the Hall of Fame, it is pretty safe to say that he will be effective for at least 6 more years. In reality, most of the players that had 10+ sacks after the age of 29 above had 10+ sacks when they were 35 or older so he should be effect for about a decade more.