What happens when I teach a set item recipe to the blacksmith?

In Diablo 3, I found a legendary set recipe called "Aughild's Treasured".

I haven't decided what to do with this item, because I'm not sure what will happen when I teach it to the blacksmith. Will all four items in the set become available for crafting? Will I be able to craft the set items indefinitely or is it a one-time use recipe? Basically, how does crafting work for legendary set recipes?

The recipe will teach your Blacksmith how to craft all four pieces of the "Aughild's Treasured" set:

• Aughild's Brow
• Aughild's Demands
• Aughild's Triumph
• Aughild's Vestments

There is no limit to the number of times you can craft each piece, other than your supply of materials.

Aughild's Treasured is one of the 2 craftable sets that use Nightmare materials (Shimmering Essence & Lizard Eye); with the other one being Captain Crimson's Attire. Interestingly, these sets do not have any overlapping parts and neither of them has a weapon (which is usually low dps in sets, cf. Hallowed Armaments) - so it is possible for a character to wear both at the same time.

All set plans, including this one, will teach your blacksmith to craft each piece in the set permanently. To learn this plan he needs to be level 6 (Illustrious).

The only recipes that need Fiery Brimstone for crafting; are the level 60 set and legendary items. Note that this also means the level 60 rare plans (e.g. Exalted Grand Vambraces) don't need brimstone, making them a much cheaper alternative in some cases.