This is a great question. Many people want to hold on to their special crafts for years to come. While there is no specialized container that you can get for origami that is going to preserve them, you can do a few things to make sure your models last.
* Store them in a dry, sealed container. The less moisture that enters, the better. Also, if you can keep them out of the sun, they won't degrade or discolor like most other paper does.
*Use quality paper. If you use poor quality, thin paper, the chances of your origami creation being damaged is greater.
* Coat your model. You can get art sprays from your local art shop and this essentially puts a coating on the outside of the paper, and it gives it protection.
* Limit the handling of the creations. I know it is fun to show them and maybe even play with them, but if you have one that you want to keep for a long time, handling it might reduce the lifespan of that piece.
Sunlight and water are going to be the worse enemies for your origami models. If you can find a way to make sure that neither gets in regular contact with the paper, then your models should last a lifetime.
Jeremy Hansen is a recognized expert on everything Origami and author of the book "Origami Secrets Revealed: Everything You Need To Know And More". For more great information like this you can check out his website at http://www.m5info.com/origamisecrets.html