How many trodes do I need to use?

I am just starting to burn carbide dies for our heading department. I am using 80/20 tungsten/copper electrodes. I have never ran a sinker.
I have been checking diameter of my finish trode for wear. When my last trode shows no more wear than .0005 I call detail good. All my burns are round.

Normally I’ve used 4 stations to burn carbide, typically no deeper then .0135" .sometimes I have to use 5 stations if top of part has a four finish called out on print ,flushing is paramount and polarity must be correct, hope that helps a little