I confess i don't do it very often. Even when i do work on a guitar like changing a pickguard or pickup or something i still keep the same set of strings. I have a few guitars which i rotate so they don't all get overly heavily played, but i reckon there's probably a couple guitars whose strings haven't been replaced for around 8-10 months. and they still sound good to me. It got me thinking about how often one should change strings. Is there a general rule of thumb?