Shooting technical expert
I am quite conversant with the problems involved in storing large numbers of shotgun cartridges in the average house.
I find the best plan is to pack cartridges in airtight containers.
I have some big plastic boxes with lids that seal tightly, although I suppose you could use well sealed polythene bags.
The important thing is to pack the cartridges in a dry, warm atmosphere before you seal them up, so that you don’t trap moisture in with them.
Don’t spray cartridge heads with rust repellents like WD40.
Evidence from America suggests that it can penetrate the primers and make them unreliable.
There seems to be some disagreement about the shelf-life of plastic-cased cartridges, so all I can say is that I have some which are around 15 years old, and they still shoot perfectly.