If you ever sharpen a blade that has an edge far inward, you notice that as you travel in from the outer tip -that the edge does less work. The inner edge just needs the grass basically cleaned off of it and it is as new. They say that the majority of the grass is centrifugally blown outward.

ok so that kind of makes sense. so shall i just forget about sharpening more inwards on the blade?

I am quite certain that i do it wrong and even more certain my way works.

I spend an entire 2-3 minutes before each mowing touching up the blade with a Dremel. Not with their mower sharpening attachment, i just use their orange stone or i have some diamond tipped sharpening stones for the dremel. I keep the entire edge knife sharp and notice a huge difference when I am in a hurry and don't bother.

How much will it help? who knows. Can it hurt anything? don't see how. if you sharpen it once and it stays razor sharp then it did not matter much, if you start sharp and it dulls then it made a difference but I love a razor sharp edge.... One of these days I will but a high end mower but my neighbor has a top of the line $800 mower and I have a piece of crap and I get a better cut - makes him nuts