I was wondering whether Ben is on the Island during "LeFleur" events so I kept looking at different time constants in Lost past till I came to those conclusions.
Ben must be on the island sometime now but he just hasn't appeared. Sawyer and other in the past cannot kill him because he is still alive in 2007. I am saying that he is on the island because when he had the tumor and Jack saw the x-ray, he said that this x-ray belongs to man in his forties. If we say he is forty, then his birthday comes on December 19th so now he is forty-one. If we go back then he was born on 1963. We know he came to the island when he was 10, so that was in 1973. I am depending on Jack's medical experience but he may have missed and Ben might be in his late thirties. Therfore, we can assure that Ben is arriving REALLY soon on the Island if he is not there yet.