My guess is that books don't have a "set Rule" for WHEN they change the Favorite's number. In other words, say most books are dealing a football favorite at 6.5 Minus varying amounts of juice, not simply the standard -110. I haven't exactly followed over the years but have surely seen -6.5 -120. My question is at what point will they just move the line to -7? OR, would they rather move the juice up to (i don't know) say -200?