In 1990 I bought a keg like that of Herco that had been originally sold in the mid 70s. It was a partial keg of about 7 pounds and already opened. So at that point, it was not yet quite 20 years old and it all burned up and performed just fine. Took me about 4 years to use it all up. And that's when I was shooting IPSC every week plus the monthly match.