I think there should be some kind of logic that makes a player less likely to sign an extension, or possibly increase demands, as the final season of his contracts draws toward the end.
As of right now, I wait until the last possible minute to resign guys to extensions, to make sure they don't suffer serious injuries, etc. In real life, if a team strung along a player like that, the player would be much more likely to test the free agency offer. How often do you see guys signed to long-term deals during the playoffs.
Not a huge deal, but I can think of a major negative to it, other than possibly owners taking over a neglected team mid-season getting screwed.