Anyone that has been into the shop knows we take humidification seriously around here. Because wood is porous, it's inevitably affected by the environment and humidity level. Acoustic guitars are prone to warping, cracking, sinking, and weather checking due to hydration issues.
Our repair department constantly sees bowed necks, acoustic tops dropping, fret ends sprouting, weather checking on finishes, and even body cracks from drying out. So here we'll address what we consider to be the most reliable way to avoid dealing with any of the above-mentioned repairs!
The best way to maintain the integrity of your guitar is to keep it in a room that stays between 40-50% humidity. This can be achieved by way of a humidifier in the room that adds moisture content. Here at the shop during the winter/dry months, we keep a humidifier in every room to control the environment for our store stock. We also recommend keeping any acoustic guitar in its case with a humidifying device to provide it with a source of moisture. More on this later.
During the summer we don't have to do much but do recommend running a dehumidifier in areas that are typically showing humidity levels above 50%. My basement at home, is a perfect example. Necks quickly bow backward when the humidity climbs, with the middle of the neck swelling, pushing towards the strings. Until a fret actually touches the strings, muting them out and effectively silencing your guitar.
Many people don't want the humidity levels in their house in the 40-50% range. Windows fog over and it's kinda gross to be breathing muggy air all the time. So rather than have to control an entire house, it is much easier to control a hardshell case. We carry a few products that do a great job of stabilizing the humidity inside your case but none is as effective, easy to use, and 'hands-free' as the D'addario's Humidipak!
This product is as easy as it gets. It maintains proper moisture levels in your case until the packets dry up. It's a two-way desiccant that can add or subtract moisture, depending on relative humidity levels. How do they do it? I don't know! I am not a scientist but I have seen these work for 1000's of guitars across the mid-west, a notoriously difficult region for wood guitars to survive. While this is typically an accessory for an acoustic guitar, we have seen highly figured necks on electric guitars to be more prone to moving with the weather. We recommended keeping a set of humidi-paks with an electric guitar in these cases as well. 
With a constant source of moisture for the guitar to feed on, any guitar will be more stable. Your neck will move less. Your top will not shrink or swell. Your fret ends will not sprout. Your action will not drop to the fretboard due to a sinking top. Your dark fingerboard will get less ash-y looking from drying out. In other words, every part of your solid wood guitar will benefit from having something to sip on!
Head to the D'Addario Website to learn more from the maker. The Humidipaks are our #1 selling SKU so if you need advice, to learn how to use them, or to order them in bulk for your collection, let us know and we will be more than happy to help! For more information on exactly what happens when your guitar dries out, check out our video made by Matt!