Grave weapon deck question

[Franzoid]

Just played a game today (as the heroes, that's a first) and we were burning through tons of zombies during the game. I got wondering if you are supposed to reshuffle the grave weapon deck when it's used up or not. I know you reshuffle the zombie deck, but the rules make a big deal out of the fact that the grave weapon deck is NOT the zombie deck.

Is there something I missed, or can you actually run out of zombie weapon-toting madness?