Mending is a treasure enchantment meaning it cannot be found in enchantment tables ever, and can only be found from chest loot, fishing drops, trading, and raid drops. It is a very exclusive enchantment because it makes your items last indefinitely.

Does mending wear out?

Simply put, a Fishing Rod equipped with Mending will never break and rarely (if ever) need to be repaired or maintained. One important note: Mending is mutually exclusive with Infinity.

Does mending have a limit?

The maximum level for the Mending enchantment is Level 1. This means that you can only enchant an item with up to Mending I, and nothing higher for this enchantment.