Mint Set Plastic Safe?

I've got coins from the Mint from as far back as the 50's and so far no problems of any kind. Of course in a few hundred years that may change so I'll let you know then.
Now here is a warning. If you have coins of any kind in any kind of plastic holders and they get to close to a fire, the plastic could melt all over the coins. However, that is no real problem since you could still sell them as coin paper weights.

The attempt to add a glue or other sealing substance to the edges of a Mint Sealed product could possibly lower the value considerably. If noticable, many collectors would suspect the container has been tampered with and the coins inside changed.
I've found the best thing for any coin type storage is to place the object in a Zip Lock type bag, press out as much air as possible. I do this with all my Coin Albums and as far as proof sets or Uncirc sets, just one big plastic bag for a box of them.
Pending on where you store any coins the invironment could become a problem. I keep most of my coins, except the ones in safe deposit boxes, in a basement. I use a really great electrical dehumidifier and the humidity stays low all the time. That, plus the Zip Lock bags does the job and has been for a long, long time.