If you got these in an auction a few years ago, who knows how long the prior owner(s) had them or how they were stored. Then you store them for a few years under unknown (to us) conditions - so they could be wearing quicker than if brand new. Typically, I'll wrap new tires for future use in a heavy duty compactor trash bag to mitigate the effects of aging.
When I bought the tires they were inside a large closed box with other tires. Since they have been in my possession they have been hung up inside, in a dark closet. Do you wrap tires in a bag to protect from UV? What kind of breakdown would cause them to wear quicker? Someone else mentioned they looked like they might be "hard", they feel plenty soft to me, and definitely grippy on the road.