My system for aging is mylar bags. The main blend I age is Luxury Bullseye Flake. I've found that just a few years on these coins is heavenly! I prefer to purchase LBF in the 1.5 pound boxes, I actually just put the whole box, into a mylar bag, push as much air out as I can and seal them. I date them with both a sharpie and a printed label, then into a plastic tote that resides on top of my pipe shelves.
I tend to only store away bulk blends in mylar. For tins, I wrap around the outside of the joint between the lid and the tin body with a product called Parafilm. It is a wax based sealing tape used in laboratories. Even those pesky square tins retain a good seal 5 years on with a strip of parafilm around them. Those tins get labeled as well, both with a sharpie and a printed label on the back. I've got another tote that I store those in.