NASA: Hold onto those glasses
Posted August 22
St. Louis, MO — Hopefully you held onto your eclipse glasses, because NASA says they are still good for future eclipses.
While they know some glasses were printed with expiration dates of three years, NASA says those warnings are outdated themselves. If the glasses are free from damage or any scratches on the film lenses, they are safe for use.
But for how long? NASA says "indefinitely"
So long as the glasses adhere to the ISO 12312-2 standard, then the glasses are safe for future use.