I am about to travel throughout S. America and am trying to book flights in the most logical/ least expensive way. I have heard in order to enter some countries I need to demonstrate that I am eventually leaving. Additionally, I believe that booking flights in advance is cheaper than not but am afraid I will be traveling, fall in love with a place and want to stay one or two days longer than anticipated thus throwing off one leg potentially by a day. Does anyone have any suggestions on how to maintain cost effectiveness while not hamstringing myself to rigid flight times? Between October 7 and early/mid December I plan on Houston-Lima-Cusco-El Calafate-BA-Bogota-Houston. Any help is appreciated.