Hank Knight
Bill, like others, I rely on tactile signals to decide when I need to touch up an edge. I think there are a number of them that, taken together, tell me that my edge has degraded to the point it needs to be refreshed: the edge doesn't bite into the wood instantly, the shaving is not contiguous across its width -i.e., it comes off the iron in long shreds rather than one continuous shaving, the plane is harder to push, the surface it leaves is not crisp; and there are probably others that I haven't recognized or articulated. All of these are subtle and occur before the edge is terminally toast. They tell me that I need to stop and sharpen. I can feel and observe them while I'm working. I don't need to interrupt the flow and rhythm of my work to disassemble the plane in order to visually inspect the edge to see if it is worn and needs sharpening.