WAR after age 31 and 32 for pitchers (top 1000 in career WAR, 30 in 2000 or more recent):
Schilling, 6.2 WAR at 31, 27.5 WAR 32-35, 23.8 WAR 36-40
Mussina, 5.6 WAR at 31, 20.6 WAR 32-35, 14.6 WAR 36-39
Halladay, 6.2 WAR at 31, 25.0 WAR 32-35
Sabathia, 3.5 WAR at 31, 3.7 WAR 32-35
Hudson, 4.7 WAR at 31, 12.5 WAR 32-35, 4.4 WAR 36-39
Verlander, 1.1 WAR at 31, 15.1 WAR 32-35
Santana 4.6 WAR at 31, 0.1 WAR 32-35
Oswalt 2.4 WAR at 31, 6.7 WAR 32-35
Colon 1.4 WAR at 31, 3.1 WAR 32-35, 10 WAR 36-40
Zambaro 0.1 WAR at 31
Lee 4.8 WAR at 31, 21.2 WAR 32-35
Peavy 5.3 WAR at 31, 4.1 WAR 32-35
Wainwright 6.2 WAR at 31, 8.2 WAR 32-35
Lackey 1.8 WAR at 31, 2.0 WAR 32-35, 9.4 WAR 36-38
Beckett 5.8 WAR at 31, 2.3 WAR 32-35
Weaver 3.0 WAR at 31, -1.6 WAR 32-34
Carpenter 5.1 WAR at 31, 10.1 WAR 32-35, 3.7 WAR 36-37
Zito 2.6 WAR at 31, -1.5 WAR 32-35
L Hernandez, 1.8 WAR at 31, 3.4 WAR 32-35,
Millwood 2.7 WAR at 31, 5.6 WAR 32-35, 1.3 WAR 36-37
Burnett, 2.4 WAR at 31, 6.7 WAR 32-35, 4.5 WAR 36-38
Hampton 1.5 WAR at 31, 1.2 WAR 32-35
Washburn 1.2 WAR at 31, 6.3 WAR 32-35
Shields 4.1 WAR at 31, 4.3 WAR 32-35
CAREER IN PROGRESS:
Grienke, 9.3 WAR at 31, 8.3 WAR 32-33
Hamels, 4.4 WAR at 31, 7.9 WAR 32-33
Scherzer, 6.1 WAR at 31, 7.3 WAR at 32
Lester 3.1 WAR at 31, 6.2 WAR 32-33
Price 1.7 WAR at 31,
Cueto, 1.8 WAR at 31,
Cain, -0.7 WAR at 31, -0.8 WAR at 32
E Santana 1.2 WAR at 31, 10.0 WAR 32-34
Kluber 8.0 WAR at 31
One thing that jumps out, most pitchers who were effective at 32-35 are "horses," guys with multiple 200+ IP seasons.
The second thing is top flight pitchers are different, they're more likely to have longevity and bounce back.
The rest are huge gambles, for every Cliff Lee there are two guys like Weaver or Beckett
And there are some freaks who actually improved with age like Colon and Lackey, but good luck predicting those.