How long of a line can the typical pencil draw?

depends on the hardness and how its used - i have a HB with a thin hard lead that i have been using for laying out drawings that has been in use about 2 years now - and then i use solid 3/8 inch thick graphite 9B pencils that go in about a week

I just tested it with my 6th grade class. We drew a line for 1/8 of a mile and it used 1/8 of the pencil lead. This reasoning means that we would use 1 inch of a pencil for 1 mile. Thus, the average 7inch pencil can draw 7 miles of a line. This does not take into account any variables such as the thickness of the lead, the pressure of the writer on the pencil, and the imperfect line that was drawn. However, I think it is safe to say that the 35 miles myth seems a bit far-stretched.