I have no experience with waxy maize but it is my understanding that white flours do not have the nutrients to sustain bacteria growth, and waxy maize not being a a whole grain (with vitamins and aa's correct me if I'm wrong)it shouldn't go bad either. I would imagine whole grain flower could go bad if very moist, either through bacterial or mycotic infection.
In my younger dumber days I did in fact grow some trippy shrooms on whole wheat flour!