Believe it or not, this is not a great idea. First off, it can be a safety issue if you are using a case that doesn’t lock. It’s always better to keep a firearm in a secured location, like a gun safe. However, the bigger issue is moisture. Most cases feature padding or cloth of some kind to protect the finish of the firearm. That material can also hold moisture which can corrode and rust. Thus, cases are meant for short term transport to and from the range, and are not an ideal long term storage solution.