It all depends on how much you practice and on the type of strings. On average, if you play guitar every day, we’d recommend changing your strings every 2 – 3 weeks. After that period, you’ll probably start noticing the first signs of wear. The overall sound will become duller and less crispy. The basses will be less resonant and will start showing fret marks above certain frets, while the trebles might feel rougher under your right hand due to microfractures.