Minecraft Java Edition – How to Make Tools Indestructible

Enchanting!

The unbreaking enchantment will make your tools last longer by adding a chance that using it will not decrease its durability.

Repairing!

Placing two of the same tool in the crafting window will combine them into one item with 10% (of the original maximum) more uses! The two original tools must also be made of the same material.

Warning: Repairing enchanted items will cause any enchantments to vanish!

Truth be said, sacrifice some time working with non-enchanted tools to build an XP grinder, and then enchanting anywhere below 30th level becomes pointless - simply reaching that 30 becomes so trivial that top-level enchantments become cheap. I do have quite a few iron tools enchanted at 30, simply because diamond became far more scarce than XP.

So, in short, the answer to your question may depend on how you obtain your XP; if you plan to build an XP grinder, there really is no point to hoard it until then, use up whatever you have. OTOH, if you plan to skip all the easy XP collection techniques (mob grinder, bulk cow/pig breeding, mining Nether Quartz, or building a hundred furnaces over a lake of lava and turning a desert worth of sand into glass) you'd better keep saving.

(still, enchanting normal materials equipment with cheap - lvl1-5 enchantments is cheap enough that it might be worthwhile.)