It all depends on how you play and how you train. I train 3 hours of mostly multiball drills + 1-2 competition once in a month. I would say it might be equal to 4 hours per week, but I suppose that I hit pretty hard and all rubbers usually die quite fast.
K3 is approximately 1 week feels quite hard (a little bit to hard for me) , than it feels much softer.
Its slight tackiness lasts up to 1 month, I think, but don't really pay attention to it
It feels really good for me up to 4 month, maybe slightly losing its speed, but rather slowly.
It is probably not that good after it, but I can play with it for 1-3 month after it, but don't enjoy it very much. So record is 7 month, but usually I switch it after 5.
And even this is better than mx-p which I used before (I enjoyed it for 3 month and than played 1 more, and it changed its feel literally every training)