About 10 years ago I thought what if I needed an item while on the road. I travel the road so I keep watch of changing things weekly. So after 10 years I went to retrieve it. Unknown what to expect, all was just dandy. Now what did I use? I got a surplus 155 Howitzer, powder canister, it has a rubber seal and is made of heavy steel with a tighten down dog/leg type method I did put a small desiccate pack in as well as things that would rust corrode etc. I did dip the lower half into bright Rustoleum paint to see it and add protection. I put silicon on the seal tightened down the lid buried it 2 feet below surface in a sandy loom soil. Over the top after bury and before refill I placed a cheap bright dog food bowl over the whole top , edge down. Well short story is when I got home It opened easy ,was dirty, dog bowl was fine and the contents were in perfect order. 10 years in the ground. I think it would go 20-30 years. I don't think (I) will however!, and the area was starting to progress, it was time . But I was amazed that it was in such great shape. I still have a 95 gallon yellow hazmat drum buried, I will wait longer for this one as I have shown my kids were to find it, so if I kick off , OH WELL can't take it with you. What do you use to stash Items?.