It would work like this example. You add a player on November 18. You can't drop him until November 25.
There are too many players getting dropped quickly and, thus, there's often little historical data of value to review and pick apart when deciding if the player might be a good pick up. Kinda dilutes the fun for me when too many players are being dropped quickly by impatient managers.
I see your point, but I also love seeing premature drops in mystery card leagues. I've taken advantage of this so many times, and always called the bluff that managers may think that the owner who dropped the player "knew something" when they really don't.