Is it bad to have lots of onEnterFrames running concurrently?

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Only recently have I understood that onEnterFrame creates a continuously-running program that runs at the same framerate as the movie (until you call a "delete enterFrame). So, if I have a bunch of these running at the same time will I see a big speed drop? I’m a bit leery about using onEnterFrame because of this. Are there any alternatives to this method? I haven’t been able to find any (short of putting onClipEvent handlers on movie clips).