Once nice thing about 45/70 is a slight but fairly straight taper to the case, which means you can totally control brass to chamber fit simply by backing off the die adjustment in the press.
One the anvil.....they don't necessarily last forever, though the point of your analogy is taken. An experienced blacksmith can easily tell the difference between a "dead" anvil and a good one. Over time, heat and beating kill the temper and for precision forging purposes, they have a lifespan. At the end of that lifespan, a few pounds of 2F and a length of cannon fuse can make quite a show!