Is the Lifetime Third Builder worth it in Dragonfire?

Yes, if you play seriously over time. The third builder (an offer around €9.99) is one of the rare PERMANENT purchases: it doesn't reset between Reigns, unlike buildings and research.

What it changes:

• +50% build capacity (3 queues instead of 2), every Reign, for life.
• You climb toward Tier 10 faster, season after season.
• The compounded effect over dozens of Reigns is enormous.

The Dragonfire investment rule: anything permanent (Gold, Relics, the third builder, Heirlooms) deserves your money; anything that resets (resources, temporary levels) never does. The third builder ticks the right box.