The shelf life on the EC-776SR series, 3M part number 7100008736. DigiKey part number 19-7100008736-ND.
This is the information from the data sheet below.
Standard shelf life for 3M EC-776SR Coating is 6 months from date of shipment when
stored at 60-80°F (15-27°C)
Data sheet link:
EC-776•EC-776SR Data Page.qxd