More pitch count.
Cho, I would certainly not argue that 120 is an arbitraty number. My point is that until pitchers turn, say, 24, their arms are still developing. It would make more sense to gauge pitch counts, but we'll have to accept innings as a reasonable proxy.
For established guys, I'm all in favor of not enforcing arbitraty rules. Randy Johnson, Curt Schilling, etc., guys who are established workhorses, their pitch counts are going to be different than for others. My point is more about young guys. As for Kerry Wood's injury, that's sort of my point. When guys are young, their arms aren't yet mature, so they're more prone to be damaged, especially by funky pitches. (I don't know why this is the case, it's just that the numbers seem to bear it out, and it makes some intuitive sense. Also I'm neither a doctor nor someone who plays one on TV.)
N.B. this debate started at a Giants-Cubs game last year when I criticized Dusty Baker for overworking Wood and Prior. I stand by my criticisms.
Just for kicks, lets look at a couple of prominent burnouts. Same format as the last post (that is, name, first number is age when he throws 100 innings, next is when he throws 200, next is when he throws 300--I track up to age 26).
Fernando Valenzuela: 20 21 (285 innings at age 21)
Steve Avery: 20, 20 (99 innings at age 19, 210 at age 20)
Fernando was effectively done at age 30, although he had a decent year in 1993 and another in 1996.
Steve Avery's last year with 150 innings was 1995, when he was 25.
Livan Hernandez--the jury's still out on how he'll do (and his age!)
I know I'm missing some good ones, but I can't think of them at the moment. Schlamp, who am I missing?
(Man I'm happy to talk about something other than how George Bush has destroyed our standing across the Muslim world by needlessly invading Iraq and then bungling it. Whoo-hoo! Here's to ignoring this great American disaster--"It's not Vietnam, it's worse!"--by paying attention to baseball)