Aqua, you simply purchase another spool of line and put it into the device attached to your bow.

A spool costs about 6 or 7 dollars.

Of course if the deer goes down, in say, 100 yards that's only 300 feet gone so just clip it and use the same spool again on the next arrow. 2500 feet in nearly half a mile. If a person hasn't found the deer before that they need to leave it alone and come back hours later.