A friend who recently bought Zombicide: Invader was pretty sure that you have to discard "Plenty of Ammo" cards after using their ability. He said he also checked online and found rules stating this (no idea where he found those). He stated that the word "once" in the card text was supposed to mean just that.
Is he right, though? Do you have to discard a "Plenty of Ammo" card after using its ability?
Here is an example from Zombicide: Black Plague (but the wording is the same for all Zombicide editions, afaik)