Ground whole grains go rancid in a short period of time. Under a week.
Pure white flour lasts longer about a year or 2.
Whole grains last 20+ years when stored properly in dry conditions. Even longer when stored without O2 such as in mylar with O2 absorbers.
I'm having trouble finding red hard winter wheat in the South East. Most grain mills have no wheat here and only wheat seed I can get is the spring wheat which is what we grow here for cover crops in winter.