I rarely ever change mine. They never break, and I'm way too lazy so usually its like a month at least. I recall one time when I changed em after about 3 months. The backsides of the strings were so black and rust colored it was disgusting, and there was a little tiny shiny spot every so often where the fret bar would have been. I do like the sound of new strings, but I play bluesy kind of stuff thats basically an overdriven sound anyways, so a little added crunch from nasty strings usually doesn't set off any CHANGE YOUR STRINGS alarm, so whatever.