Is "_visible = false" efficiency friendly?

basically, i’m writing a flash program that generates several entire menus of links on the fly from an XML file. i’m kind of anal about my code performing the best it can, and i’ve run into an efficiency crossroads… i’m trying to decide on the best implementation, and there’s only one thing i don’t know for sure:

if i have a movieclip on the stage, but _visible = false, is that movie clip still draining CPU cycles (accepting onEnterFrame events and such), or has it been completely frozen? basically, could i have an arbitrarily large number of _visible = false MovieClips on the stage without a significant hit on performance?