The Monster Blood City was about the same size as the Heaven Blood City. The only difference between the two cities was that the former one had two layers of shields. One of them was blue and the other one was yellow, providing much stronger protection.
That being said, no matter how strong the defense was, the shields would be cracked at some point. Shields needed the energy to support and energy was accumulated over a long period of time through formations of collections. There were simply too many alien races attacking from all cities. How much longer did the city have?
Two months and a half!
Many people had done the math. At the very best, shields of the Monster Blood City had two and a half months. After that time, the Monster Blood City would fall into shambles. All the warriors would have to retreat to the Demon-slaying City.