Use 'em and don't worry.
This tire age thing is a very successful marketing ploy.
Go to the TIRE MANUFACTURER'S website and read their
recommendations on number of years to use your tires.
Don't listen to a dealer, marketing person, or your
brother-in-law. Lot of hear-say, developed by the same
marketers that sold kids expiration dates on breakfast
cereal years ago.
40 years in the tire industry; seen it all and done most of it.