Lycanthropes are currently very rare in Eberron. However, they can change under any of twelve full moons, and can potentially transform around a dozen times/month.
Lycanthrope Species
History
Lycanthropic purge conducted by Silver Flame, particularly in what is currently Aundair and the Eldeen Reaches.
Currently
Most Lycanthropes now reside on the plane of Lammania, the twilight forest.