Much depends on whether the flavor volatiles are predominently water soluble or fat soluble. For example, in the equally old, more flavor loss seems to occur is herbs that have significant quantities of water soluble flavors (some of the mints, sage, parsley--which, to me, is horrid in dried form, galangal, savory, basil, et al.) than with those that have predominently fat soluble volatiles (bay, peppercorns, allspice, thyme, et al.). As herbs and spices age the flavors become less dimensional and flatten as the most time-, light-, and air-sensitive volatiles are affected.
Storing excess bulk spices/herbs or rubs you make in bulk vac-sealed and in the freezer will extend shelf life significantly.