James McMurray said:Durational effects in D&D are almost always assumed to end just prior to the turn. A spell with a duration of one round ends just before your next initiative. It makes sense to me that a dragon whose breath weapon is unusable for one round would follow the same rule, and recharge just prior to the dragon's next initiative.
shilsen said:One more vote for every round. I'm almost certain I saw this question answered somewhere but I can't recall where.