I'd like to get a better understanding of how Flash renders display objects, so I have a better idea of how to optimize my games.

I previously created a game that had a scrolling, repeating (and parallaxing) background. I tiled it and cached as bitmap, which was quite a pain when taking animating display objects in the background into consideration. Is there a better way to do this?

Another question is if I have a large bitmap (or vector art that I have cached as bitmap), is there any kind of performance hit if it is completely off screen? How about if it is partially on screen - does flash have to render the entire bitmap, or just what it sees on screen?