Access other class' variables

Hello Everyone,

I am making a tileMap class which copies bitmapdata from one location to another. I am storing all my tile-sheets as static bitmapdata objects in an Assets class. Would it be faster/ better practice to copy the tile-sheet I am using to the tileMap class instead of referencing the assets class multiple times every frame? Also the map array which stores the tile reference is stored as a static property in a map class, could I achieve better performance by duplicating this array in the tileMap class?

Thanks

Spir