As everyone else is saying, waaaaay beyond their usable SAFE life.I wouldn't even consider them as spares.
That seems a little conservative for a garage-kept car, assuming proper inflation and no winter usage. Sure, not for autocrossing, maybe, but 10 years should be easy for a set of low-mileage, well-stored rubber.I wouldn't be caught dead with tires on my car over 6 years old, unless it could somehow be proven beyond any shadow of any doubt that the tires never saw any sunlight.
As long as they hold air and support the car, they'd be great show tires for a concourse vehicle.These tires are far closer to 20 years old,than they are to 10 (17+ actually) I don't know what one could use them for,but they are unsafe for vehicle operation on public roads.
off topic from OP's post but FWIW:But this got me thinking about my spare tire. It's never been used since I've had the car in 1996, but it's damn near 20 years old now. It may be time to look for a replacement. . Maybe even a 17"er to match the other 4.....