I looked at the top 1B in both 2000 and 2010 and a LOT of them fall off a cliff at some point around 33, 34 years old. Guys like Pujols, Adrian Gonzalez, Miggy, Fielder, Tex, Konerko, Helton, Giambi, Delgado, Olerud...
... almost none of them are guys you would have wanted on a big contract for their mid-late 30s. Most gave their teams a bunch of negative WAR seasons and maybe a couple league average years.
I don't think many people, even certain SABR people, give age effects the appropriate consideration. They can make all the difference. When it's a 32 year old vs a 27 year old like Freeman and Olson.... I mean history tells us that Freeman may have 1 or 2 more good years before he sucks and Olson should be good for most of his contract.