But if you design a factory to make shells quickly, each production line can probably do 1 shell per second (they're not so different from big bullets, and those are made very rapidly).
11 of those lines and you can be keeping up that rate forever.
11 of those lines and you can be keeping up that rate forever.
The main issue today, is such stockpiles are easily found by recon (satellites, airplanes, drones), and then blown up by enemy artillery / rocket artillery.