CPU or GPU Rendering
GPU can work only with bitmaps. Use cacheAsBitmap and cacheAsBitmapMatrix with vector graphics is a very processor intensive process. Basically means that at every new frame this movieclip has to be converted to bitmap. Try using the draw method of BitmapData. GPU mode makes sense to use it when there is a lot of animated objects moving and interacting with each other across the screen.
Don’t create and remove the same objects, reuse them.
TextFields and objects receiving mouse events are slowing down performance. If you have objects that aren’t reacting on MouseEvents, you should disable mouseEnabled and mouseChildren properties.
Keep framerate as low as possible
if(STATE_PAUSE) stage.frameRate = LOW_FRAME_RATE; else stage.frameRate = HIGH_FRAME_RATE;
EnterFrames are faster than timers and intervals
Vector vs Array
Not use array.length in each iteration. Use a variable to store the length.