Primers can be exposed to massive humidity, dried and will go off just fine. When made, the primer compound is mixed with water and squeegeed into the cups. The compound is inert when wet, but once dry they are active. I still store mine in ziplock bags to try and maintain a constant level of humidity to keep the SDs consistant.So get this.
Just for conversation sake.
A good friend of mine had to move and gave me all of his reloading stuff from the 1970s.
He hasn't shot since about 1980.
I got a few thousand primers in their factory non sealed packaging. These primers spent over 30 years in a Virginia attic. We have four seasons here, and they change like a rollercoaster. Would you believe that every primer worked flawlessly? Doesn't make any sense to me, but its absolutely a fact.
I still stick to metal ammo cans as I stated above, and in a controlled environment. Although this ammo we all store so cautiously may be more resilient than we give it credit for. I'm not going to find out by testing the limits of ammo I spent my hard earned money on though.