So, you've cleaned your dutch oven and the camping season is over. Now, you need to store your dutch oven for a few months and prevent it from rusting and going rancid. It's not difficult, but it is important to take a few cautionary steps.
Keep It Coated - a very thin film of light vegetable oil should be applied after the last time you clean your dutch oven. You should try to rub off practically all the oil with paper towels and that which is left will help keep moisture away from the metal. With a good solid seasoning layer, the metal of your oven should be well protected so you may want to skip this if you've got a well-used dutch oven.
Leaving too much oil on or in the oven can result in a foul, rancid smell when you pull it out of storage. If that happens, restoring your dutch oven may be required.
Keep it Dry - moisture is the worst thing for your dutch oven. Try to store it in a dry location which might be your garage or basement, depending on your house. Here in the midwest, winters are very dry so I just keep mine in the garage.
Keep Air Moving - a useful trick is to prop the lid off the oven to allow a small amount of air circulation inside the oven. A good way to do this is to roll a paper towel into a pencil shape and set one end in the bottom of the oven. Then, put the lid on which should bend the paper towel over but keep the lid open a crack. This absorbent towel will help wick moisture out of the oven and keep it dry. You could use two or three of these paper towel wicks on larger ovens.
Keep It Protected - There are dutch oven bags and other accessories in which to store your cookware. I don't personally use these since my dutch ovens get a lot of abuse out in the woods anyway and nothing is going to scratch them up while they're sitting in my garage. But, if you need to transport yours a lot or you want to keep other gear clean around your dutch oven, then covering your oven would take care of that. Covering your oven, even just in a big paper bag, helps keep dust and grime off it and helps pull away moisture.
If you stop to think about it for a minute, your dutch oven is just a big hunk of strong iron. If you were to let it sit in a damp dungeon with pools of water all around for 20 years, it's going to be rusty and ugly, that's true. But, it won't really harm the utensil that much. If that were to actually happen, or if you found a dutch oven in a garage sale that looked like someone had stored it in the barn for 50 years, all you need to do is restore it. By storing your dutch oven carefully, you are just saving yourself a bunch of work next year. If you decide to just toss it in a corner of the basement, it will be just fine the next time you want to use it, but you'll just need to put in some effort seasoning it before cooking in it.