I've noticed that most people refer to number of hours before their strings break or need to be cut out. As I am currently working through several different types of strings in order to dial my game in, I wanted to make sure that I am correctly keeping track of this. My concern is that during different hitting sessions, the ball on my strings varies. This is what I have so far: Hitting on wall: constant Ball machine: constant Private lesson: constant Singles match: a little less per hour due to change overs etc... Group lessons: (usually 4 in a class) so divide by 4. Doubles match: a little less than group lessons My question is are there certain guides / rules to make sure that I am correctly counting how many hours my strings last? I noticed on this forum that the same string lasts some people 1 hr. and others 18 hrs. I know that playing styles have a lot to do with this. I want to make sure that I don't count my 2 hr. doubles match as the same as a 2 hr. ball machine sessions.