So let’s say you started laying down a Blend in 2014. It is your favorite, so you have acquired a significant amount. You have some from each of the ensuing years. Once you run out of bags from 2014, would you begin to open bags from 2015 or tins from 2014?
Your sealed tins are good for...ever.
I happen to know the blend of which you speak and people have had trouble with pin-holes in those bags (*I havent, I put them away and don't mess with them, but others have). I have also seen people post that they had trouble with the older square tins losing their seal but again - a non-issue for me so far.
If you're concerned about anything it should probably be the bags. Jar them up if they're unsettling you. Or just leave them hidden in that one secret box and move them as little as possible.
Another option is to push the burden onto a good friend who lives in the woods and will hardly smoke any of your stash.