In my opinion, there are too many variables to say you need x amount of brushes for each motor/armature. How hard you push your motors, and how many times/how often you cut the comm will be the biggest factor. Yes? Trinity's brushes, supposedly, will last 50+ runs before needing replaced. Must be a harder compound. I don't remember ever getting that many runs on a set of brushes.

Quite the collection of motors. Do you have a favorite? Curious to know what are you running them in.