3 months for a young baseball player can make a huge difference in the perception of a player. Consider Aaron Laffey and Jeremy Sowers. Last offseason Laffey was not even in the discussion about top 20 prospects in the indians organization, and Sowers just came off a superb second half with the tribe. At that time clearly they shouldn't be mentioned as comparables, but InfiniteMonkeyTypists did (see http://www.letsgotribe.com/comments/2007/2/1/161345/5869/6#6) and this was not warmly regarded.
But in the last 3 months Laffey has outpitched Sowers (and Stanford and Lofgren), especially the last month, when he has been very good at Buffalo. He is also 2 years younger than Sowers.
So is Laffey better than Sowers now? Or is 3 months of data not much to get worked up about? Does Laffey now slot in after Lofgren as the 3rd best pitching prospect? Laffey and Sowers are both junky lefties who don't strike many out, but Laffey has always gotten more ground balls.
I guess this is another example of why you get a large quantity of arms. You never know who will all of a sudden "lost it" (Sowers), and who will "find it" (Laffey). Of course, this can switch just as quickly.