Via U.S.S. Mariner, check out this important article at Hardball Times, which offers evidence in support of the tentative hypothesis that, on average, pitcher velocity starts to decline quite considerably at age 29, dipping about 4 MPH by age 34. It also suggests that velocity increases a bit, on average, from age 24-29.
Anyone who watches a fair amount of baseball knows that some pitchers lose velocity as they age, but this research suggests that it's not a good idea for teams to expect even pitchers in their early 30s to maintain their velocity. The article suggests that by performance (that is, by results, not by velocity), the typical aging patterns of pitchers are less severe than this research makes it seem, so pitchers may compensate for their lost velocity with improvements in their command or control, or just by being smarter. Still, I'd be wary of big commitments for older pitchers.
Matt Morris, by the way, is the posterboy for this Age-Related Velocity Drop. (I'm capitalizing that because it's just begging for an acronym. "Morris used to be a good pitcher, but as the decade wore on, he got ARV'D." It's particularly good because it sounds like something that would happen to a pirate.) As a 30-year-old with the Cardinals in 2005, Morris' average fastball was 89.1 MPH. It dipped each year after that, and this year it was 85.9, at which point, as we all know, he was basically throwing batting practice.
Of course, this all should have been totally obvious to anyone in the Pirates organization who even bothered to check out his games on MLB.tv before the trade. Maybe Dave Littlefield doesn't know how to use a computer?