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. You can either have infinite arrows or a Bow that can be repaired; you won't be able to use both without using cheats.

Does mending make tools last forever?

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.

Why did my pickaxe break mending?

The reason for this is that with each XP orb, one item with Mending is picked at random out of the items you are wearing or holding. If that item is fully repaired, the XP goes towards your level - another item is not selected. If this is in fact, a fact.