Like the title says, how often do you scuff, pick or shape your tip?
I just did it for the second time yesterday since I got my new tip put on several months ago. And I think I did that because I had nothing else to do that second and remembered I found my tip tool and stuck it in my bag.
It would really depend on the tip you have. The Ki-Tech one I got put on has not needed any work at all to touch it up. Stayed in perfect shape since it was new.