An equivalent period of time in the past would pre-date decipherable writing, possibly the invention of writing altogether. In other words, this is silly. Migh

An equivalent period of time in the past would pre-date decipherable writing, possibly the invention of writing altogether. In other words, this is silly. Might as well throw away the key and just say "never open it", the effect would be the same. Such an insane period of time is isomorphic to making the thing a tomb or an archaeological site.