Does the Undead Warrior lose its two boost tokens at the end of every turn, or only when a unit is destroyed?

Question

Accepted Answer

Two tokens are lost at the end of every turn. Boosts are gained for each unit destroyed on your turn, so the Warrior can be loaded up on turns when several units die.

Summoner Wars (Second Edition)

Does the Undead Warrior lose its two boost tokens at the end of every turn, or only when a unit is destroyed?