Max screen size with Teensy 4.1?

I am using a Teensy 4.1 + SmartLED shield to drive multiple P5 64x32 panels. So far I have 12 panels chained giving a total screen of 192x128 px, working great! I would like to add more panels to make a bigger screen. How large could I go (in theory)? What are the main limiting factors and what can I do to mitigate them? I am not using any animation, my display is just showing text and rectangles. Thanks!