There is not supposed to be an expiration date….
Check it out:

Florida Senator Marco Rubio told National Rifle Association members Friday he believes the country is at a turning point on national security and the Second Amendment.

“We’ve all heard it said that the usefulness of the Second Amendment has run its course – that the purpose it served in the days of muskets no longer applies in the days of AR15s,” he said. “But the genius of our founders is not milk – it has no expiration date. It is more like wine – it gets more valuable with the passage of time.”