In Michigan it gets dry indoors in winter. Yes, humidity affects electric guitars because all wood is hygroscopic (absorbs or releases moisture). As it swells and contracts from adding or losing moisture, stuff happens to setups, finishes, fretboard shrinkage (the fret end problem), etc.
It’s true that PRS does a great job drying their wood. However, the wood can still absorb or release some moisture over time when it leaves the factory.
I use a humidifier and throw a D’Addario humidipak into the case of my electrics (in a spot it can’t get squished, like the headstock area or an opening beside the neck in most cases). One guy at D’Addario told a friend he worries about the humidipaks getting smooshed in a case; however, another tech there told him to do what I do, just put it where that can’t happen. Humidipaks absorb and release moisture to keep the case at around 45%, which happens to be the RH at the PRS factory (yeah, I asked).
You are obviously aware that all guitars need fewer adjustments and do better if put in their cases when not in use. This is because the case buffers the many humidity and temperature changes that occur in a room during a 24 hour period; the guitars stay clean, and dust doesn’t combine with stuff like the cooking oil evaporates present in a house to goo up your controls and make them scratchy, etc.
Lots of folks here don’t have issues, but over the years this has kept my guitars in great condition. I have never needed a seasonal adjustment on a PRS since I started being careful about humidifying the room and keeping everything cased a couple of decades ago.
