The label on the marinade says “Best when purchased by 24 Dec 03.” So, is just purchasing enough? Will it still be good, considering I haven’t opened it almost four years later?

Food items I’m fairly sure came with me when I moved to this state, and still in my cupboard:
blueberry muffin mix
cake mix
jello mix
chocolate pudding mix
two cans of tuna

I think I’m taking this concept of non-perishable too far. I was even ashamed to give this stuff to the post office food drive.