Not quite.  NIP-03 is only half the problem.  It is proof of publication.  It shows something existed BEFORE a certain block.  The next part is solved in something like Peter Todd's "after_btc_block" : "hash".  Now you have AFTER and BEFORE, which is a time period.  The final part is to repeat this for the next period creating a provable audit trail in time, with continuity.  For a global "save game" you would need to pay, depending on how much security you wanted, but we are talking about 1 sat baseline.