Does the quality of a steel change toward the the top of the knife vs the edge? I sharpen my knives often and some knives just don't cut the same as they used to, and I'm not really sure weather it's because my edge is getting thicker at the top and needs thinning out or if the steel just isn't as great towards the top of the knife. I'm assuming that it's the former, but for some of my knives, they feel completely different from when I 1st got them, making me believe it could be the latter.