With Starling, the issue may be with how the images are being loaded.
The most efficient way to load in image assets for Starling, is in ATF spritesheets. For desktop, you’d use a pixel format of DTX5 (or DTX1 if alpha isn’t required).
Use the Starling AssetManager to import these at runtime, don’t embed them. Textures can be referenced by many things simultaneously (similar to how BitmapData works), in Starling’s case you would usually use a container like an Image or MovieClip if it’s a sequence, to reference Textures.
Then, when these elements enter the screen, overhead should be relatively low. It’s simply a case of having a container like an Image or MovieClip reference Textures that are already loaded in the GPU.