Some aging pitchers gradually lose steam and others go over a cliff. But I have noticed that the same often happens to pitchers regardless of age. The shelf life can be short, and in any given year, injury seems more likely to factor into what kind of year a pitcher has than anything else, including age. So if you are looking at established ML pitchers and are going to look at the risk of having a worse year than the one before, you really need to be looking more toward IL stint history than age. I consider a guy who just did 32 starts to be a good bet.