I was able to do it 75 times until it was completely unplayable. And by unplayable, I mean 4.83 fps unplayable.
Generally, I don't let US2 drop below 10 fps, but when I want to push what the sandbox can do, dipping below that is okay. In fact, when I paused the simulation, it gave me a few more frames, which was about 6.50 to 7.00 fps. Just enough to still move the camera, albeit, real slow.