Seeds have a longer shelf life than many people expect. The only thing that I know of that’s pretty limited is onion seeds. They’re supposed to only be good for one year, but I easily got two out of them.
Here are some links to seed viability.
From the Farmer’s Almanac (they say 1 year):
How Long Do Seeds Last?
https://www.almanac.com/how-long-do-seeds-last
The Spruce is another good site for gardening info. (they say 6 years):
How Long Do Seeds Last and Are They Still Good?
https://www.thespruce.com/how-long-do-vegetable-seeds-last-1403089
Many thanks to both of you for the links and the great advice! The seeds are the loose-leaf variety, and I’m going to plant them tomorrow. Will report back on how they do. Fingers crossed. :-)