You've just experienced what kind of blades I've been working on with my WSKO! Beaten to death blades that take longer because the edge is essentially flat. In many cases you can't really even call it an edge anymore because it's so flat and blunt.
You'll get used to judging this by examining the blade before you start. I look for a reflection on the cutting edge. The more easy it is to see the reflection, the more dull and flat the edge is and the more work it will require.
The good news is you got a respectable edge on that blade. Good job.
Brian.