If you want to clear all of the pins of the leads map so your reps don't see their pins next year or the next time they knock through an area, go to customers->leads->view all.
Hit the actions button on the right and hit the red "Delete all non conv. leads" button. It will clear "Not Interested," "Not Home," and the "Leads" pins, all of which are considered "non-converted leads." You will have to have Owner or Branch Manager Admin privileges to do this.