The original Power King teeth ground six 14 to 24 " fresh cut pine and oak stumps before needing replacement. I then installed the Green Teeth. Be careful the first few couple stumps as these are very agressive!
I have ground 14 additional 20 to 28" stumps with the Green Teeth and am still on the first cutting edge. I have 17 stumps to go and then I'm done with stumps forever!
An added note: I am 77 years old, arthritic hands, with two torn rotator cuffs and this is quite a struggle for me. But I have been able to do 1-1/2 to 2 stumps per day with a couple days rest in between. One day I did 3 stumps in 4 hours. If I can do it, anyone can.
Get the Green Teeth, you won't be sorry!