Hi springy,  shoes in general are notorious for deteriorating over time, worn or not.

Had a quantity of golf shoes a while back,  new in box, were from a sports store closure, all high quality brands.  Took  over 12 months to sell them all and all was well, except for the last pair to sell.  First time used by the buyer and the inner lining disintegrated.

Nothing to do with shoes, but also had a shipment of high quality brand, adventure tents.  $1000 each retail

New in original packaging and were selling like hot cakes, then it was found the inner waterproofing was disintegrating.  All sales were refunded and they got to keep them, now that was an expensive exercise.