How do you store the individual factory loaded rounds? Do you leave them in the cardboard boxes or coordinate into larger containers in the metal ammo boxes or even mass dump rounds into the storage boxes?
Simple answer: yes
I do a bit of all three, but with factory ammo, I mostly leave it in the boxes it comes in, and put them in an ammo can. My reloads are either boxed (plastic) or loose, in their cans.
I used to use the 2.75" rocket crates for mass storage of boxed ammo, but unfortunately learned that when half full of 44Mag and half of 22LR, lifting one throws my back out, and it takes months or more to come back...
So, I have made an effort to standaize on USGI .50cal ammo cans. Even packed completely full of ammo, I can still lift or carry one without injury.
The .30 cal cans are very nice, and a have a few, but decided to go with the .50 cans for the most storage and versatility. Not quite as easily portable, but most useful for me.
Modern smokeless powder will degrade with time (even when properly stored), but it takes close to a century or so, if the powder was properly made. Note that ammo produced under wartime conditions wasn't expected to need a long shelf life before being used, so it may degrade sooner.
Militaries excess and dispose of their unused ammo after set time periods, because they can, and consider its cost as part of doing business. I'm kind of cheap, so I keep mine until use, or some obvious sign of degradation.
Have handloads decades old, and still fine when used. Have GI ammo pushing the half century mark, and have faith in it still. And I have fired ammo from WW I era which all worked.
TO counter this, I have a stripper clip of 6.5X55mm Swede headstamp 1897, which has cracked brass and degraded powder. Have had a lot of WW II ammo not fire (examples from all nations)
I've been storing ammo in GI cans for decades (after all, its what they were made for), there is nothing better. Cans in good condition (seals, etc) can stand submersion for a while (depth will change the amount of time) without leaking. In a fire, the sturdy can usually contains the fragments from the detonating ammo, they have ruggedly sturdy latches, a convenient handle, and gosh, they just look so good.....what's not to like?
And since I live in a low humidity area, dessicant, while always a good idea, hasn't proven necessary for my home storage ammo, for a long, long time. Now, if I "can" some ammo on the coast, dessicant goes in, automatically.