I was wondering, what should the behaviour of an interval action be if duration is set to zero? I would think that it would become an "instant action", meaning it would run instantly and then be complete.
I looked at the api docs
http://www.cocos2d-iphone.org/api-ref/latest-stable/interface_interval_action.html
and also noticed there's an issue posted about ensuring duration is never set to zero:
So it seems that the thought is that it shouldn't be allowed to be zero, but I can't see why. It seems like it'd be a nice way to have an action that can be either instant, or have duration.