Here is a site concerning white rice. Bugs that you cannot see can still be in the rice. If properly stored polished white rice can last for 25 to 30 years. But then that's properly stored.

http://extension.usu.edu/foodstorage/htm/white-rice/

Flour is another one that I leave in it's package and put it in the freezer to kill any bugs that might be in there. These are bugs and such that you can't see. Just bring it out so that it can come to room temperature when you want to use it.

I keep some flour in a covered container - flour that I use really often.