It could be the type of wood your cutting & splitting. When my ax hits in my sand and rocks a few times the edge is gone. When the edge is gone, that means it takes more exerted energy to obtain a split. I guess it's just my wood. DM
I would only have to dull my axe or maul once by running it into rocky ground to figure out that I needed to be doing my splitting on a stump or block of some sort, how long is it going to take you to figure that out???