It's been a while, but I think the math question stops after you've made enough posts/replies. 50 or 100 or something like that.
"This young wine may have a lot of tannins now, but in 5 or 10 years it is going to be spectacular, despite the fact that right now it tastes like crude oil. You know this is how it is supposed to taste at this stage of development." ~ Itzhak Perlman
@risk String changes are pretty different time frame from pretty much everyone you ask. lol. I know i change my strings when ever i start hearing my strings sound more "dead" like they have lost some of the tone they produce, or if i start seeing areas where they are weakening or if i want to try a new type of string.
I know i've heard that if your a professional player that plays hours on end a day most change theirs out anywhere from every 6 weeks to 3 months and I've heard for those who are beginners/amateurs you can go about 9 months to a year if your only playing an hour or two a day.
But i just go by the sound and look of my strings. hope that wasn't to confusing of an answer!
some more experienced people here might have a better answer for you but thats what i've found for most of my playing anyways.
Lead me, Follow me, or get out of my way!
~General George S. Patton