Welcome to the fun world of firearms. I'm not hooked. Really. I can quit any time I want. So far I haven't wanted to in almost 55 years but I could quit.

One thing and this is serious. What type of case did you buy? Unless it has foam specifically designed for long term storage I would NOT keep anything in it for storage. Cases are for taking the gun to the range. At least most of them are. The kind that doesn't hold moisture in the foam is a lot more expensive. The foam will hold moisture right against your gun and there is a very good chance it will cause rust to appear. Sometimes it will cause rust in a matter of days. I've known of people that put a brand new gun in a foam lined case and left it there 6 months. When they opened the case they found a totally rusted gun.

The M&P Sport II seems to be treated pretty well so rust shouldn't come easy but those cases are the absolute worst place for long term storage. That would even apply to aluminum mags IMO because they will have a steel spring inside. Foam kills firearms. You could very well end up with a gun that looks like this if you store it a Plano case or anything not designed to deal with moisture.