If UK or Duke offers a sophomore, they usually get that kid. And the crystal ball guys know it, so when those offers go out they immediately pick said player to land at UK or Duke -- which pumps up the "average days" metric.
This is starting to apply a little bit to UConn as well -- a bunch of guys picked Reeves to go here when we offered him the other day. If he eventually signs with us, they'll look prescient. But it's really just a smart bet that almost anybody who follows recruiting could make if they wanted to.
I personally think the national guys (even Meyer & Evans) aren't all that knowledgable, and it's the local guys who are worth following. Slater (the dude who has a Duke blog) just picked Bolden to Kentucky, for example. And he picked Waters to Duke the day before Duke offered him.
Anyway, I think the crystal ball is a hell of a lot of fun, but you have to take it with a grain of salt. Recruiting is fluid.