Line contact styli have a much larger contact area than conical or elliptical types because they fit more snugly in the groove and contact more of the groove from top to bottom. Not only did J. Carr provide the numbers, the chart clearly shows this as well (line E of the chart, and the illustration on line D).
What is critical for line contact type cartridges to work properly is good alignment. Azimuth is particularly important. I have also found that vta/sra is also important (small changes can be heard).
AsFor wear, with proper care and clean records, I easily get at least 1500 hours on the cartridges I’ve owned. Way back when I used elliptical cartridges, I got MUCH less hours of use (but it was cheap and easy to change styli). Of course this might be attributable to other causes (like the quality of diamond used).