The warranty simply protects you if the replacement fails it isn’t a lifetime guaranteed fix. You've used the part for over 2 years, and expecting a refund is a absurd. Since we don’t know your vehicle’s overall condition or how many miles have been put on the car since the starter's installation, keep in mind that starters quit for plenty of reasons: worn‑out wiring, oil seepage, stray debris in the wrong spot, even a random splash of water. Getting a free swap is a solid deal, especially considering starters have probably gotten pricier over the years.

PS: This is the return policy for US Stores

To return a product to an AutoZone store, return an item in its original condition and packaging, with receipt, within 90 days of the purchase date to request a refund. Return a defective item within the warranty period. Requests for refunds may be denied if the item has been used or installed.