The lots that have been posted how long ago were these lots made
I'm just guessing, but I bought 5 boxes (500) primers about 5 years ago. I also bought 3-4 boxes about a year later. I'm not sure which purchase had the bad ones, because I would just grab a box and use it when needed.
Then I bought a carton (1000) primers about a month after buying the 3-4 boxes. They are replacing/paying for (I'm not sure which) what is left of the single boxes (about 250 primers) and the unopened carton (1000).