ok what i understand is, to answer your first question, is most cases can be reloaded several times, as long as there is no sign of tearing. belted mags like the 7mm rem mag you won't get near the life out of them. then there is the deal with just neck sizing vs full resizing. neck sizing can prolong the life of your brass. brass inspection should be done every time before you reload.
the second question is a bit perplexing. shooters will reload lake city brass which is military. now that case ammo for the ars, aks and the like often times isn't brass. i think its tin or some cheap metal, and can't be reloaded nor can you reload the aluminum. nickel can be reloaded but its a pain.