There are several options for board storage based on the amount of storage space you have to work with.
Ideal scenario is that the board is stored inflated at roughly half pressure (4-6 PSI) in a cool place that does not have exposure to large temperature changes or direct sunlight. The boards are least susceptible to damage when the air pressure inside of the chamber is greater than the air pressure on the outside of the board.
If you don’t have the luxury of enough space to store the board inflated, the next ideal scenario is to deflate the board and store it loosely rolled with the valve pin up and cap on. By “loosely rolled” I mean that there is enough space in between each layer of the board roll that you can fit your arm in between. This will make sure that you aren’t over-flexing/creasing the sidewall material and possibly creating weak points in seams. The boards are very susceptible to damage when deflated. Dragging, even the slightest bit on semi-abrasive surfaces like concrete or asphalt, can cause major damage to sidewalls where the material is folded. This isn’t an issue when the board is inflated. The reason you want to make sure that your valve is sealed is because the only opportunity for water (humidity) to make its way into the inner chamber is when the board is deflated. If storing in an area that can reach below freezing temperatures, this can be a problem due to the expansion of water when it freezes.
Many people store their board tightly rolled in the bag – we recommend against this. While the bag can protect it from wear and tear damage during storage, you’re setting yourself up for potential seam blowouts or sidewall damage down the road. Generally, you don’t want to have your board rolled tight enough to fit in the bag unless you are traveling with it.