I change when my strings when they break till they cannot break. Haha.. I got a floyd and it usually breaks at the bridge, so I just take the stump out and reuse the string. Once there is not enough string material to secure the string on the post I will buy a new set. That was when I was on .009. Since I changed to .010 they have not broken yet, touch wood. I'm currently using black diamond black coated strings, and I polish my strings with DR string cleaner. This way I can use a set of strings for months, always sounding good, always brand new. Only gripe about BD is that they flake, but when the string tarnishes it still looks kinda black, so it doesn't make a difference to me haha